Thanks Joseph. The product I selected was quartz with eased edge. I did not like the location of the seam proposed - it was just to the left in parallel to the sink. I asked to have it moved to under the cooktop on the one side of “L” shaped countertop (other side has sink and dishwasher). The updated design was to have cut outs at each side of cooktop - basically a separate piece that would connect the two pieces under the cooktop at top and one at bottom - where cooktop would have lip over counter. From your comment I’m not sure if you are saying this is “bad”?

I wouldn't assume that the floor joists are sufficient. They usually are merely sufficient to meet code minimums. Code minimums are actually pretty pitiful when it comes to being able to support anything real. Most will need to actually be reinforced to be stiff enough for tile or other hard surface floor coverings. You need to research the length, depth, and span of the joists underneath your kitchen. Enter the information into the Deflectometer (Google it) and you will probably find that they need sistering or cross bracing. Or both.

Yep, likely from heat, which is ridiculous. I have a very similar crack on my quartz countertops that were installed April 2020. I recently used my crockpot on the counter and the crack appeared off of the seam just like yours looks. I am so upset. I was told by the installer that I could put hot things on the counter, but a quick google search after this happened shows that is not true. The installer is telling me it must have gone from super cold to super hot very quickly, this is not the case at all. They will not help us at all and it looks like i will need to get the corner piece replaced.

I wouldn't be happy with it either but you asked for eased edge and that is what you got. The rounded corner has nothing to do with eased edge. When I met with the fabricator I brought pictures of everything so there was no misunderstanding. I had picture of how I wanted the edges, inside corners and outside corners.