Having hardware powerful enough that third parties can just throw existing code at it without spending any time on optimisation and it 'just runs' with maybe a slightly better anti-aliasing solution or slightly higher resolution VFX than a PS4 or X1 title wouldn't exactly hurt their third party support.
It doesnt work like that. It never has and never will.
Even if the machine is comparable in power, there will be different OS overheads, input methods to support (doubly so if we believe the entire rumour) and other quirks to the system.
I have no problem with the idea tha Nintendo is bring things closer to the other consoles in terms of hardware, but extra power does not mean it will "just run", nor does it suggest higher resoultions or AA as plenty Console ports on PC can readily attest.
To believe that the NX is a more powerful system than both the PS4 and Xbox one is to also believe that Nintendo and third parties are planning to put in more time and investment into their games to use that extra power.
As in the previous generation, most werent even bothered to make competent ports and Nintendo themselves only really focused on performance, I find it very hard to believe.