I upgraded (as opposed to clean installed) W10 on a number of systems (using a clone of the original drive before refitting the original drive).
Two of these systems were a Core 2 Duo and a Core 2 Quad which originally came with Vista 32 bit. Both run W8.1 64 bit with no apparent problem and upgraded and ran just fine. So unless the Anniversary update has some seriously bloated new features I wouldn't expect any problems.
Not that I intend to run W10 on any of my systems any time soon (if ever).
I have no idea what the author was chuntering on about.