You're absolutely right OP, don't let anyone tell you otherwise.
For all of you guys who enjoy trading, you'd still be able to trade with a single version. No one is stopping you. My two friends who play it and I all ended up buying Sword. Newsflash: we are still allowed to trade with each other, so I can confirm trading within a single version is still enabled, despite what I've heard on this thread. But guess what: we'll never complete the Pokédex! Trade as much as you want. But if other people can't (or don't want to) trade, why should they be forced to? Why not make their lives a little bit easier, by removing the possibility you buy the same version as your friend?
If having all Pokémon accessible in a single version makes you stop trading - well, I guess it was never fun in the first place then!
I bet a lot of the people who support the idea of two versions are the same people who went mad over "Dexit". And then complained about how bad looking and archaic, and easy the games were. But the Pokémon fan base gets the game it deserves really. If you want a game with good production values, good progression, and innovation, you should try embracing modernity across the board. Dropping outdated practices is good, and GF should absolutely drop the two versions thing. But no, the fan base is averse to progress, so yeah, beating the Elite 4 will become ever easier, completing the Pokédex will become increasingly impossible if you haven't been playing for the past 20 years, and the games will look worse and worse compared to competitors.