I didn't get the impression from the article that "being sidetracked" had anything to do with it -- it sounds like he constantly has multiple projects going on.
The issues were twofold -- he had heard that same study about magnets close to the head issue, and is looking into it (also shielding, and then the weight problem); and amplification (ribbons, of course, require special amplification) -- I'm assuming it's the same issue as with ribbon speakers -- I.E. the low impedance presented across the frequency spectrum, but have not received confirmation.