This looks somewhat interesting --
https://www.kohlershowers.com/
Appears to use a cultured marble or similar "composite" type material to cover the walls, they call is "LuxStone"...
Apparently this is an "offshoot" of Kohler's "walk-in tub" business --
https://www.kohlerwalkinbath.com/walk-in-bath-features/ . That strikes me as driven much more by folks with a desire for "aging in place" and from what I've experienced with elderly parents / in-laws (as well read up about...) these are massively over-promoted...
Buying A Walk-In Bathtub – Your Biggest Mistake? | homeability.com
I've used Kohler products before, and they generally are well made, but I wonder how others feel? Even the most costly "kit showers" generally strike me as not as good a choice as traditional materials.
Personally I would be extremely reluctant to consider anything other than a shower that was fully tiled / covered in natural store and walk-in tubs have ZERO appeal to me...