Yeah, I figured something like that. L. Zinn recommends such long crank arms for taller riders.

By all means, try them! If you feel stronger and faster, you are stronger and faster

That said... I don't buy it any more. At one point I was convinced crank arm length should be proportional to some measurement, such as the rider's leg or something, but the more I experimented with it, I lost that conviction. I'm now persuaded that the bike industry is basically right, that one crank arm length works, more or less, for a rider of any size (just as people of just about any size can use the same staircase without complaint).

At the same time, I'm also convinced that road cyclists generally use cranks far longer than ideal. Granted, the disadvantage of long crank arms is negligible, but there is no advantage at all. YMMV, of course.