Did you ever determine what Swanstone makes their's out of? It seems it should be very similar to Corian.

The only information I can find about swanstone is it's a "a revolutionary and compression-molded solid surface material."
Stains and scratches can always be buffed or sanded out - no gel-coat or laminate surface to wear away like the onyx collection.

Which sounds like properties of acrylic but also heat resistant.

I found the Swanstone Technical Data Sheet, which says

Product Composition: "Swanstone is a compression-molded compound that consists of a blend of polymer resins, fillers and reinforcement additives. In the manufacturing process, Swanstone transforms into a thermoset material that has extreme resistance to heat, impact, expansion, and chemicals."

While at Swanstone, I did look at the subway panels. They do have a pretty good look to them, on the screen. I believe I saw them in person once and my only concern was that they do not have the shiny look of tile, instead looking very matte. Also, there is no differentiation in texture between the "tile" and the "grout" on the panel, so it has a fake look to it. But, as my mother used to say, "a man on a galloping horse wouldn't notice!" It does have the solid and classic look of tile at a quick glance.

I did look up all of the solid surfaces on your list and found a Hi-Macs ADA roll-in shower pan that is 36 x 60. This is bigger than the Swanstone one that has me worried about its size. So I do have another option available without a custom order price tag. Thanks for holding this discussion on solid surface shower walls!

Yes a matte finish and no difference between the dull tile and grout line is cheesy. That's why I was hoping to find a acrylic panel with gloss, but I will not find anything with a grout line that looks authentic.

I remember my dad had a surround that was a single panel tile look alike. It had gloss tile, and then the grout lines were routered in. Like T1-11 plywood. It was two different materials. Color gloss outside, and cream matte inside and looked great. I cant seem to find it and not sure if it was acrylic but it definitely wasn't solid surface.

I had panels like that put into my bathtub surround on my previous house as a temporary fix. I was preparing to move in to the fixer upper I had just bought and was standing on the tub, disassembling the shower doors and as I was unscrewing the aluminum track I must have leaned against the plastic tub surround. It was not properly affixed to the wall and was loose and as I leaned on it, it flexed inward, pushing air out the top of it. I got a whoosh of heavy mold/mildew smell when that air hit my nose and so I grabbed the top of that plastic surround and yanked and it came right down. My studs were rotted out, there was so much decay behind that thing. I went to the lumberyard/home center and they had a product called Baker Board that was meant for bathroom walls, but not inside showers. I hired a guy with good skills for measuring and cutting and gluing, because after he replaced the studs and put up greenboard, he put this Baker Board up for me on all three walls and the ceiling of the bathtub alcove and really caulked the seams well. I hoped to be able to put up ceramic tile in a few years. We never did, sold the place 20 years later and the Baker Board had never leaked. Mine looked like 4x4 tile. I never scrubbed the stuff, was gentle with cleaning. If I had not just done asbestos abatement and put in new ducts and replaced the furnace, I might have been able to do tile, but I was just broke. I married a year or so later. Over the years we replaced everything in that house except the roof and that bathtub surround!