Cadence, like bike fit inflation pressure, is optimized for 28 year old professionals with 1% body fat. Not for MAMIL's riding with their mates.
CLEARLY, like most things biological, there is a range of what works. Probably 70-110. Oh yea....that is for a flat course on a warm, windless day, while drafting, after proper warmup, but not fatigued, being well-rested but fit and nourished, but not too much and hydrated, but not too much. And, fully caffeinated (but not too much).
One more thing....is that with a waxed chain or wet lube?