I rode in this position for a good hour out in front of a race last year. You do get bruised forearms. But like the football players, your body will toughen up and stop bruising if you hit it in the same spot enough. In other words, if you train in that position, you'll get bruises, but then they'll go away and not return.
The "invisible aerobar" position for me has my arms on the bars at mid-forearm with my right hand holding onto both shifter cables (Shimano pre under-tape routing) where they cross and my left hand holding the top of my right hand. I can hold the position for an hour and even did a TT in this position in a stage race when I didn't bring a TT bike. I feel it is more aero but less powerful than holding the hoods (with flat forearms) or in the drops.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter