Bingo! Cadence is as much about cardiovascular efficiency as anything else. A high cadence will push up the heart rate if you aren't conditioned for that rpm. There also is the concept of slow-twitch/fast-twitch fibres and the apparent drop-off in the effect of fast-twitch fibres as we age. But then, fast twitch might well be about 150rpm cadence... and not so much 90-100.

I think the OP is a bit optimistic. Either thhe A-grade group he is running with is a pretty weak one, or he is pulling our legs.