I can see how it would be fine on a TT or tri bike with aerobars, but I don’t see how anyone can ride a road bike with the 1. saddle tilted down 2. the knees well forward of the BB 3. extreme bar drop/reach (see Adam Hansen’s current position for an example).
This would be a perfect storm of factors that make it impossible to hold yourself into the seat without using your arms. Regardless of how strong your core is, physics should dictate that you would be falling out if your seat without significant pressure on the hands.
If you had a seat that was level and had your knees above or behind the BB, I could see how you could hold yourself up in an extremely aero position just from core strength and very high watts/kg.
Do the pros simply deal with the potential hand and wrist pain for the aero benefits, or am I missing something? Is it really possible to will yourself into such a position on core strength and watts/kg alone?