Are you using someone like INest?
If the builder put in plumbing top out, the house is close to ready and they are ready to close the house. They probably don't want to have to go through the hassle of taking out the tub, chipping out the tile (?) tub surround, ordering a new tub, installing it, having the plumbers uninstall and install the tubs, re-grout the tile area, etc.
Do you still want the house? If so, go up the food chain at the builder's corporate office if you can't get it changed with the sales counselor or builder there onsite. Go to the project manager, then the VP, then the President of the Region, etc.
If that doesn't get you where you want, tell them you are going to file a grievance with the Texas Residential Construction Commission (TRCC) and then do so.
If it makes you feel any better, builders will not let you put EM or options money in escrow as if you decide not to buy the home, they would not have any recourse to get the money. The builders feel like they are taking the risk for building a $300k (or whatever) home and the homeowner is putting down something like 1% or less.
If you have decided to let go of the home, then contact your Realtor and let them know what's going on. If it's one of those type of firms where you never meet the person, you can just call the office and let them know what's going on. They're not going to get paid at all if you don't buy the home, so they've got a vested interest in this. See if they'll be willing to do anything on your behalf. I also know an awesome RE attorney who does speaker work with Stephen Covey, but don't think he works on flat fee.
Contact me if I can be of further help.