The last time I installed one of these, I came out with brass nipples through the tile that I was able to seal around. But then the homeowner had the entire shower tiled so it wasn't up to me either.
It did make for a nice clean job.
I may have installed 90's after it left the tile and pointed them down for the flex connectors. There's room behind the panel for the flex connectors to hang.
It seems to me, that there is the possiblity of using something like clear polyseamseal where the stainless unit meets the wall on the sides.
I would not seal the bottom of the unit. If water gets in there, you need an exit for it.
There is a hanger attached to the wall that the shower panel hangs to. It's very easy to lift it off if needed.
Most plumbers don't do tile. And most tile setters don't do plumbing.
There are a few that I work with, and I love following them on their jobs. I get to do my thing, and they get to do theirs.