The claim apparently stems from developers who have received dev kits for the NX, who said that what they saw couldn’t possibly be run on a computer that didn’t have top-of-the-line chips; however, they didn’t elaborate on exactly what “cutting-edge” meant. The unnamed developer that the person who started the Nintendo Forums thread claimed to have spoken to even said that one of the demos included in the kit was “currently impossible to run at 60fps using a current-generation Intel…CPU and a nearly top-of-the-line graphics card”.
Of course, we aren’t likely to hear anything official on the subject for quite a while. Even if these claims are true we must keep in mind the fact that none of this is set in stone yet, since the hardware won’t be finalized until sometime much closer to the console’s release date.