Tile no, grout it depends on the type of grot. Typically this would be on the tiler to avoid finger pointing issues potentially down the road.

Forgot to mention the house is being built by a production builder. So sounds like I'll need to seal the grout lines then.

Ask before you do because at least here that is a sub-sub-contractor who is a specialist. You do not want to apply a sealer if another has already been applied because it might cause a really bad mess.

And remember: as soon as you ALTER the work done in the house, YOU OWN that work and anything that happens there after.

Imagine having a tiled floor that cost $15/sf to purchase and install. You go and do something like seal the grout lines. Now imagine 6 months later the grout starts to crack and the tiles start to lift (I can't tell you how many times this scenario has occurred). Guess what the builder is going to say, "My guy's work was just fine. Your mucking around with the grout caused the issue. I can fix it but it will cost you."

In other words, the failing install will be put back on the LAST PERSON who touched the floor. And THAT'S why you do not touch anything that is still under warranty. Not until the warranty has run out. After that, have at'er.