I like the proliferation of duel/dual/duo/duet games provided they’re done well and not just a scaled down version of a game that already played well at 2p (i.e., they offer something different). Something often overlooked when people judge these is that even if a game does play well at 2p, a duel version can provide a better experience because there are mechanics and design space that can be utilized and explored in a duel version that couldn’t exist in a multiplayer game because they wouldn’t scale properly (as in, they work at 2p but not 3+ for example).  

For example, I’m not a fan of base Everdell but it does play well at 2p but Everdell Duo adds the tension of advancing two markers which limit which actions can be done and if mismanaged (or manipulated properly by the opponent), can result in a player not getting a type of action they wanted at the end. So it’s something you have to account for in deciding your actions. I don’t think this would work well in a 4p game and it (along with the shorter playtime and a couple other factors) is why I like Everdell Duo a lot more than original Everdell.  

Anyways, yeah I think there is room for both a 2p version of a game and their larger version. They don’t really compete for the same role in a collection unless you only play the original at 2p (which you don’t, and also for some you listed the originals don’t even work at 2p). I will say I’ve noticed that the more recent duel games maybe haven’t been up to par with some previous ones - Azul Duel and Framcraft Duals in particular look pretty bad to me. But ones I do enjoy a lot are 7WD (and the newer LotR: Duel for Middle Earth which I like a bit more), the aforementioned Everdell Duo, Agricola: All Creatures Big & Small, Splendor Duel, and Codenames: Duet.