I gotta say, this is very commendable for a third party developer that not only understands the key features of the Switch, but embraces them to the point of making sure the game(s) they are porting is the best it can be.
The Witcher 3 probably was expensive to port given the depth and complexity of the game, itself, and the 32GB cart. I have given my support for CD Projekt Red by buying the Switch version (though I have not played it yet). I hope other developers who are considering porting games on Switch will take note on putting some more effort on these port developments. Hell, take DQXIS as another example of a competent port on Switch. The Switch audience want great games on Switch just like on any other platform. Ports are not a bad thing. Just make sure the port is competent and runs the best it can on the platform it releases on.
Third party games can succeed on Switch if the third party developers are willing to go through the process of development the right way instead of half-assing it or just doing for a quick buck (i.e., FIFA, some of Capcom's ports, Ark: Survival Evolved, and WWE 2K 18). If it doesn't work, that's fine, don't develop it any further.
FWIW, The Witcher 3 is in the top 10 of the best sellers list on Nintendo Switch's US eshop (based on what I saw recently) so I hope it means its doing well.