Portable-only games that need touch to function are good for the Switch right now, and don't undermine the concept at all. One, not too many people even want to play those types of games on the big screen, meaning the work necessary to convert them into a motion/buttons experience would likely go to waste. Two, since Nintendo is still going with the "It's a home console" PR spin, touch-based portable games can easily be spun as an extra bonus, further driving home the point that this is a system not confined to just your living room.
Dock-only games do undermine the current perception and selling point of the concept though, and I wouldn't expect to see them until much later in the Switch's life, if at all. But if the Switch performs well, the option of sqeezing every bit of docked power it has without worrying about portable mode might seem like a good idea for some western devs looking to get extra sales. By then, Switch would (hopefully) be mature enough as a platform to fully embrace the hybrid concept by having extra benefits to both home and portable play (exclusive games), while still keeping the majority of the library usable in both modes.