I don't see anything in either code that prohibits it. P2705.1 of the IECC Residential code (2015) doesn't appear to mention it at all, and the UPC 412 (from 2018 at least) is about Urinals (whether or not a shower constitutes a urinal if you pee in the shower is out of scope of the UPC). :) UPC 408.9 mentions it this way: "Control valves and shower heads should be mounted on the sidewall of shower compartments or otherwise arranged so that the water does not discharge at the entrance of the compartment so that so that the bather can adjust the valves before stepping into the shower spray" So nothing to do specifically with the thing pointed at the door, moreso can you turn on the water without being sprayed by it, which is a good idea anyway since that first blast is likely to be quite cold.

Add this to my previous: If the glass will be pulled, then work out the scope of work and responsibility ahead of time. In writing. In a perfect world you'd have the glass company come out and remove the glass, then when the repairs are done, they come back out to reset the glass. That'll usually cost $$$. That money does not come out of your pocket. Your tiler can pay for them to do that. He may insist he can do it himself, with the caveat that he is accepting full responsibility for damage to any of the glass panels. And that's where the problems arise. Will he pony up $500 or $2500 for new glass if he shatters a panel? I'd let him have that responsibility only after he gives you a deposit of the $500 or $2500 that the replacement glass would cost. The glass breaks, you have cash on hand for new glass. If the repairs go fine with no damage, he gets the full amount back.

is the tile already installed? If not , you can leave channels/rabets/dado for the glass to sit into. You can also just have a very close fit and it probably won't be too bad. Steam is dense so it's not going to rush out of a small crack at the joints, it will escape so it depends on the rest of your design as to whether you can work with this. The weather stripping looks horrible and kinda defeats the purpose of frameless IMHO. Glass guys offer standard advice: frameless and steam showers aren't good company. It can be done, but you really need to design and refine all the details from the outset. Sounds like maybe you waited too long to involve the glass people or the steam generator was an addition.

You have a workable situation very similar to one we encountered a couple of years ago when we had a frameless shower door installed in a renovated bathroom. I would HIGHLY recommend that you have a professional do the installation from the measurement, ordering, and final installation. Due to circumstances I won't go into, an installer who did not make the initial measurements tried to do the installation for our project. He was unable to make the shower door work. To make a long story short, it took several months to get it right. The good news was that we had worked with a reputable kitchen-bath showroom who stood behind their product so we didn't suffer any loss other than the inconvenience of the delay. Had we been the ones who had done the measurements, I'm afraid we would have had to absorb the financial loss of a quite expensive shower door.