It's likely referring to the Realforce keyboards, notice the title says "HHKB _and_ Realforce", then "Mechanical Programming _and_ Gaming Keyboards", respectively.
The layout isn't the problem (or at least not just), I'd just never recommend Topre for gaming.
Why not?
They don't actuate very rapidly, and they take quite a bit to reset. Probably fine for casual gaming, but I wouldn't try A-D strafing with them.
IMO, intensive keyboard games should be played with left hand auxiliary keypads, any WSAD is silly. It should be Razer Tartarus or Azeron Cyborg or whichever the current option.
Ugh. These are rarely as good as real keyboard in my experience, and they take up space on your desk. I play competitively and I still have never found a use for these - real keyboards all the way IMO.