I forgot to mention that my tub is 66” long and is wider at one end than the other. Here’s a picure of the model from the store I purchased it from...

There are a few. I went through this with a client a few years ago, you need to go to a real plumbing showroom and explain your predicament. As I recall the one we used had everything contained above the floor. This one choice will decide all you other plumbing choices.

We had a small wall built and then mounted a tub filler on it. Our freestanding tub is 4" from the front edge of the wall. The tub filler reaches into the tub by about 4".

Perhaps you could substitute a tub that supports a deck-mounted filler (example)

"...most wall mounted fillers don’t have a long enough reach to fill the tub"

Twelve inches!

I think it is possible you just have to carefully plan ahead and the rough-in needs to be measured out and completed prior to the floor being poured (sort of the same when you have a tiled floor - the rough-in is done at the subfloor stage and the fixture install is completed after the tiling and grouting is complete). Consult with your bathroom faucet supplier as well as other plumbers. Tell them
how thick the concrete will be and what the sub-surface is.

@Sharon Brindley Designs "I think it is possible you just have to carefully plan ahead and the rough-in needs to be measured out and completed..."

How is this possible? He will have a concrete slab. For example, clearly both the American Standard rough valve for freestanding tub faucets and and Kohler mounting block for bath fillers cannot be just buried in concrete.

I went with a wall mount tub filler

Here’s an update to let everyone know how it turned out. I’m happy with it, although I would’ve loved a hand held shower with it. (I couldn’t find a wall mounted tub filler with a diverter, so a hand held shower wasn’t possible).