I think it became unified because portable hardware became faster relative to home hardware. Even if they had a Series S device, you can still consciously choose to unify your software platform, since it takes 18 times more GPU performance to get from 720p/30 to 4k/60, there is still much to offer people in terms of upgraded Switch visuals while still having a base Switch game.
What you said earlier about your "experience matters" is so true. For example I paid a fortune for Virtual console titles on Wii U. Still use it all the time. Not only did my purchases not carry forward, I can't even buy most of them for Switch. Zelda: Minish Cap!!!
Meanwhile my Xbox / 360 / One / and Series X purchases are all shared...
Yeah the way Nintendo handles retro game right now is atrocious.
As to a Series S like dedicated console that would play Switch games at 4K, would that sell enough to justify its costs? I don't think it would as the hybrid concept is such a key part of their current hardware's appeal.
Bet with Liquidlaser: I say PS5 and Xbox Series will sell more than 56 million combined by the end of 2023.