There's nothing in the paragraph you quote from Ortofon that settles the issue of how the Quintet, in particular, is constructed. I did read Fremer's review of the 2M Mono SE, and it's a top candidate for me; I agree it seems to have been designed to eliminate as much as possible signal induced by vertical modulation. Finally, my recollection is that, using a test LP, Dudley determined that the Grado produced more "noise" resulting from vertical modulation than did the other 2 of the 3 mono cartridges under test. He then speculated that perhaps it was less adherent to true mono construction than the others. However, when he listened to the Grado on mono LPs, it more than held its own for reproduction of actual music, as compared to the other two. Perhaps that's the part of his review that you are thinking of. Look, all I'm saying is that as audiophiles, we might be interested in knowing exactly what we're buying when we buy a mono cartridge. And as for me, were I to purchase the Grado, I would use it with the mono switch on my preamplifier engaged so as to eliminate, or at least further attenuate, even the last bit of noise produced by vertical modulation of the stylus tip.
By the way also, the Lyra mono cartridges, at least the Helikon and the Delos (and probably by inference the Kleos), seem to be among the few historically that really are true mono. Too bad they cost so much. You're also right in saying that mono LPs are becoming very a la mode, and perhaps this trend has indeed induced the production of better mono cartridges, such as your AT.
By the way also, the Lyra mono cartridges, at least the Helikon and the Delos (and probably by inference the Kleos), seem to be among the few historically that really are true mono. Too bad they cost so much. You're also right in saying that mono LPs are becoming very a la mode, and perhaps this trend has indeed induced the production of better mono cartridges, such as your AT.