In my experience using Samsung G9 OLED displays, I'm very sceptical. The perfect blacks of OLED displays are elevated on my G9 OLED when light hits the display surface at the wrong angles. And the finish of my G9 OLED isn't even attempting to be anything other than glossy.
I expect Apple's nano-coating to leaps beyond the plastic finish on my G9 OLED, but still. The good thing about these OLED panels is that they have 1000 nits of all-screen brightness for both SDR and HDR. And 1600 nits peak brightness for HDR. With such luminance, you don't put the 0 nits blacks on as much to create great contrast. This will allow the nano-coating to elevate the black levels without the display feeling far worse, like on my G9 OLED with only 400 nits full-screen brightness and 800 nits peak brightness.
However, judging by the nano-coating on the XDR Pro Display, it will affect contrast by elevating black levels. This is bad for OLED displays as they usually provide perfect black levels. You are sacrificing picture quality to get a display finish that is less affected by ambient light conditions. It sounds like something suited for particular purposes when you add how easily the nano-texture gets smudges and whatnot. And this is most likely why it's limited to 1TB+ options only, and not the default option.
I was considering getting the nano-texture for the 1TB version anyway to get the fully featured M4 SoC and additional RAM. I don't like how the 256GB and 512GB models are limited by getting less CPU cores and half the RAM.