Did the reduction from 15 to 12 rounds enable "modern superheavyweights"?

I def think there would be SHWs with steroids and PEDs. It’s only they may weigh less come in trimmed for 15. Think AJ and Fury did the opposite of what they should have done against Usyk. Should have came in more trim to increase their work rate to match him a bit better.
I don’t think shws would be able to compete at the rate they are if they didn’t have PEDs.

 

Better athletes with broader recruitment across the globe.

We live in the best of all possible worlds for heavyweights.

 

I think they've likely contributed to more extremely tall men being able to develop the athletic capability required to compete successfully at world level, yes.

That and a growing population in general, of course.