I know how you feel! I had originally gone with a highly recommended tiler who refused to do a pre-slope underneath a liner. When my husband referred him to the TCNA guidelines, the tiler's response was that he'd been doing it his way for 30 years and there haven't been any leaks. Obviously we weren't happy with that answer and cancelled the work with him.

Ultimately, we found a tiler who uses Wedi. He rips out tons of showers done improperly without a pre-slope, etc..

I've learned to listen to that inner voice of discomfort -- if a pro is reluctant or combatant to answer my questions, they're not getting my business. Happier for both of us.

I think you’re confusing a GC with a tile contractor. They are separate entities. The GC has the overall whole job responsibility, and brings in the plumber, electrician, framing crew, and tile subcontractor. In many locations, a tile contractor does not have a contractors license. Depends on location.

The one guy does it all type of contractor is exceedingly rare. Not just because of requirements for licensed plumbers and electricians to do that work, but because it's rare to find someone who can do all equally well.

There’s a lot more unlicensed hacks out there that do tile than there are really good licensed tile contractors. And a lot more GC’s that never heard of the TCNA than have heard of it.

To find good folks, search correctly.

https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer

You not asking anything unreasonable. As to why he not using industry standards, some people out there who were in business for many years and they just haven't learned anything.

Show him this

and this

Good luck.

Is there anything int the contract wording in regards to how exactly the shower was to be constructed? In progress pictures may help us determine if you need to cut your loses and start over before you end up with a giant rotten mess................................