I highly doubt Nintendo is attempting any kind of gap closure with the deck, because how could they and why?

The only thing they share is a form factor. Nintendo is well aware that the reason they sell consoles is as a dedicated platform for their own games. I truly believe that is their bread and butter and all they really care about. If the system gets popular enough, then it will get some third party support which means it will have some very limited library crossover with PC/PS/Xbox, but I think we are past the point where Nintendo intends to rely on that as a selling point for this or any future generation of consoles. Ports of games that come to switch are pretty uniformly the worst version of the game to play, and it's pretty clear that doesn't bother Nintendo at all.

Which is all to say, I don't think Nintendo and Valve think of each other as direct competitors, because they serve entirely different markets. I have both a switch and a deck. I love them both. I use my switch to play Nintendo games, I use my deck to play pretty much anything else. I don't think I'm unique at all in that regard, and frankly it never would occur to me that these devices have anything to do with one another.