that doesn't change the fact that it is a tablet with a screen on it.
handhelds have consistently added more and more features and characteristics of home consoles. that's the natural evolution of handheld systems. the original limitation that made this not possible was just the technology being not available or too expensive.
that didn't stop companies from trying it even back in the 90s tho
the PSP 2000 and 3000 could be connected to a TV, because Sony knew the games they sell on their handheld in combination with the technology they had available, meant that they could make the PSP a viable system for people to use on a TV.
with the PSPgo they went a step further and added Dualshock 3 support and sold a dock to make connecting to a TV even better. it also supported local multiplayer for PS1 games.
so clearly the steps in the direction of making the handheld work as a home console were already very apparent.
with the PSVita they apparently removed an HDMI port during development because of a hardware issue. the data lines and a spot for a connector are still there on the 1000 model.
but later they of course released the Vita TV/PlayStation TV, which allowed you to play Vita games on a TV, and some Vita games also supported local multiplayer on a single system for that reason.
Nintendo simply went for the next step in this clear direction that the handheld market is going. and they used this opportunity to also unify their development studios so that they don't have to spread their games across 2 systems, especially when they both are able to deliver similar experiences anyway.
next gen we will probably see at least Microsoft follow. they will most probably have a Handheld that takes the spot of the Series S, and I would also bet that that handheld will be able to connect to a TV and controllers.
recently even rumours of a Sony handheld surfaced, which if it will be made, will probably also follow that trend.
the Steam Deck can be used as a fully functional PC, as can the ROG Ally or the Lenovo Legion.
all of them play the same games as home consoles and PCs. not because there is some deeper design philosophy behind that fact, but simply because the technology allows it now.