Don't line them up. Start with a joint in the center of a tile close to the center of the wall, and go out to the two sides from there, so it gains or loses symmetrically. That's the only way to go about it and make it look half way decent.

Yes, staggering the sheets, but there's actually more to it than that (how you trowel the thinset, etc. and control your grout joints). Sometimes even pulling the pennies off and hand setting at the sheet perimeters . Techniques that an experienced professional understands. We don't know the material and how it was mounted so without all the information.....

that actually looks pretty good! what you want to make sure of is to get consistent spacing between the sheets. even though you stagger them, you have to make sure there is adequate spacing. what I've circled is where I see the tiles too close together. That's what's going to give you the lines. also too large of space between sheets will also be noticeable. Anything that is different is going to be noticeable! just be cognizant of that and try to replicate the natural spacing. using a grout that is close to the tile color will also help. it's difficult. just take your time when setting them. if you have to take a few off the sheet, then do so. sheets that are too far apart are just as noticeable as sheets too close together. sometimes cutting the sheets into diff strips (instead of just staggering the sheets) will also help to break up the grid-look

"they said used a liquid sealant on the floor and a foot up the wall. I hope it’s enough." Nope. Every inch of the cement board needs to be covered. All joints taped with a non-alkaline tape and spackled with thinset. Floor needs to be sloped 1/4" per foot and as mentioned it does not look like it is sufficient. Screw pattern looks of as well, and judging by that container on the floor, probably drywall screws to boot. No wonder he has no idea how to lay that type tile.