Actually, good chance the wood DID dry out. As it dries it contracts, which would explain the cracking tile. One way or the other, there's movement due to moisture getting to the framing, whether it's from being wet and drying, or after drying out, it's now getting wet again. Either way, it never should've been covered up wet. You don't know how long it was wet, and how much damage has been done top the wood. Sometimes, there's more damage than can be seen while it's wet. No real way to tell for sure without opening up the wall, but then again, it's certainly a moisture/ movement problem involving the framing, and the only way to solve that is to pull it all apart and redo it.

Get the builder in and express your concerns to him ASAP. Let him know this is NOT due to settling, that being that the shower pan is only connected to the structure at the drain, there should be no movement in it sufficient enough to cause grout to crack and especially not to come out. Ask him if he knows for CERTAIN that the bench was waterproofed, and how. Does the pan membrane come across the front of the bench, or does it go under? One way or the other, something is happening there that shouldn't be, and it needs to be fixed, and not next month.

PPF: All materials have a coefficient of linear thermal expansion. Coefficient of linear thermal expansion for concrete is roughly the same as for iron which is why it (rebar) works well with concrete. Expansion/contraction is significant for long linear surfaces such as the large concrete slab with the crack OPs thread. Though there is a much more to material science, especially concrete and types of concrete, hopefully the following excerpt provides an adequate explanation. THERMAL EXPANSION AND CONTRACTION Materials expand or contract when subjected to changes in temperature. Most materials expand when they are heated, and contract when they are cooled. When free to deform, concrete will expand or contract due to fluctuations in temperature. The size of the concrete structure whether it is a bridge, a highway, or a building does not make it immune to the effects of temperature. The expansion and contraction with changes in temperature occur regardless 0of the structure’s cross-sectional area. Concrete expands slightly as temperature rises and contracts as temperature falls. Temperature changes may be caused by environmental conditions or by cement hydration (the exothermic chemical process in which the cement reacts with the water in a mixture of concrete to create the calcium silicate hydrate binder and other compounds). An average value for the coefficient of thermal expansion of concrete is about 10 millionths per degree Celsius (10x10-6/C), although values ranging from 7 to 12 millionths per degree Celsius have been observed. This amounts to a length change of 1.7 centimeters for every 30.5 meters of concrete subjected to a rise or fall of 38 degrees Celsius. Thermal expansion and contraction of concrete varies primarily with aggregate type (shale, limestone, siliceous gravel, granite), cementitious material content, water cement ratio, temperature range, concrete age, and ambient relative humidity. Of these factors, aggregate type has the greatest influence on the expansion and contraction of concrete. Severe problems develop in massive structures where heat cannot be dissipated. Thermal contraction on the concrete’s surface without a corresponding change in its interior temperature will cause a thermal differential and potentially lead to cracking. Temperature changes that result in shortening will crack concrete members that are held in place or restrained by another part of the structure, internal reinforcement or by the ground. Forexample, a long restrained concrete section is allowed to drop in temperature. As the temperature drops, the concrete tends to shorten, but cannot as it is restrained along its base length. This causes the concrete to be stressed, and eventually crack. Joints are the most effective way to control cracking. If a sizable section of concrete is not provided with properly spaced joints to accommodate temperature movement, the concrete will crack in a regular pattern related to the temperature and restraint directory. Control joints are grooved, formed, or sawed into sidewalks, driveways, pavements, floors, and walls so that cracking will occur in these joints rather than in a random manner. Contraction joints provide for movement in the plane of a slab or wall, and induce cracking caused by thermal shrinkage at preselected locations. One of the most economical methods for making a contraction joint is by simply sawing a continuous cut in the top of the slab with a masonry saw.

They are removing the sections with the crack, if I remember what you said above, which occurs at the curve. It looks from the pic, although pics can skew perspective, that the driveway is pretty "flat" from the curve on up to the garage and stoop. My guess is that is why he called, and probably had to pay for, the surveyor to give slab elevations so he could see how far off this section of the entire drive is. Otherwise, if it were just a problem against the garage doors, he could have used a long level to find out the slope and undulations himself for free. So, my hunch is the surveyor told him he would need to remove from the crack all the way up to the garage. Which is expensive, thus the cheap sawcut in a trench drain solution. But more problematic to repour might be the stoop height, where if the concrete was sloped appropriately you'd have an odd step there. Note this scenario I have explained could be only partially right or 100% wrong, beccause I'm just guessing on 1 pic and the facts from your perspective. Whether you accept the trench drain or push for a repour is your call.