As time goes, more Switch trouble surfaces. Rime, Xenoblade 2, Nights of Azure 2 and now WW2K18... The likely explanation is that 3rd parties have never been serious in their support for Switch. Nintendo probably struck hefty deals with some of them to secure ports and that's about it, no real investment from the publishers.
The Xeno2 case is more concerning. Monolith is a great developer and they should have ample resources. So the poor handheld mode essentially says that Switch might have shown its limits as a hybrid already. And if it can't be reliable in handheld mode, I'd say its future is rather clouded.
I don't think so. I think it's more of an indicator that the game wasn't fully optimzed for docked and portable mode. Hopefully, there will be some patches to optimize the game.