Makes sense.. on mine, they added about 2" of mud on the bottom and then slopped the tile down to the skimmer. It would make sense to just talk with your PB and let him put your mind at rest. It would also not hurt if it were possible for you to be there when the tile is being installed.
I was personally amazed as to how the various trades building my pool always did things that allowed the next team to just continue along without having to go back and do something over. A very simple example: When they bent the rebar that was to tie into the decking up. I thought how can it possible tie in if it is pointed up in the air. But, when the decking crew came, it allow them the access to do all the deck drains and get their rebar in and everything prepped. Once that was done, the decking crew bent the rebar back down and tied it in the decking rebar. Not that we didn't have a few issues, but for the most part, the various crews worked flawlessly together.
Jim R.