Haha, i don't know right now. but from the point of view that yoga is a systematiztion of techniques that is useful for connecting to energy, correcting the flow of and balancing the energy in the body, and opening the channels in the body to allow it to handle higher bandwidth of different sorts of energies safely, I suppose that perhaps these great saints already knew how to do that on some level even if they weren't following sort of formal practices. Of course that's just a theory we'd have to look back into the past to make sure.

another perspective is maybe they discovered or were taught techniques even more advanced than what's commonly know as yoga. Maybe that helped them somehow attain their heights as you said.

From another point of view I think there's an idea that yoga is probably for the common people, you know, everyone. Maybe there's some exceptional people whose bodies are already highly tuned somehow and they sort of don't need to do that...could be possible. But that would probably be rare like Olympic level athlete rare. And maybe some of those great saints weren't even human. So maybe techniques for the everyperson human form don't apply to them.

Harder to speculate about those things than it is to know that yoga is good for me from experience, and have a theory for why correct yoga would be good for most others as well, especially meditators.

Aside from what i already said, biomedically the long holding, and the precise poses, sooth and calm the parasympathetic nervous system, which helps correctly regulate many other systems, and help massage and promoting flow in the lymphatic system, i think. Even leaving aside the energy perspectives, relaxedly holding poses for a handful of breaths, is a great tune up for your body.

>there's some exceptional people whose bodies are already highly tuned somehow and they sort of don't need to do that...could be possible

ya, I too have read about that..

To the best of my knowledge, the only physical yoga he recommended was sitting cross-legged, and even that was likely just because he was teaching forest medicants (among others) who could not rely on having a chair.

Yoga is only very recently regarded as mostly physical exercise. Of the 8 limbs of yoga only one is Asana (postures)

If you read Patanjali (the foundational text) there is very little or no mention at all of posture.