The Switcher 3 package has "play on an enormous world on the go" or something like that written on it. Some definitely treat it more as a portable unit, because the games seem more appealing like that.
The portability is a selling point of the Switch; it's supposed to be a system that more or less works just as well either on your TV or as a portable without having to buy two separate game libraries or add-ons like the Super Game Boy or the Game Boy Player. So you can take Switcher 3 with you or play it on your TV. Since Witcher 3 isn't going to look as good on the Switch as it does on PS4, X1, or PC, that's not a bad angle for CD Project to take to sell it to Switch owners. I own Switcher 3 and mostly play it on TV in the dock.