All the evidence required is the mass of the object and the total kinetic energy the second stage can add to the object - rockets are like that: they don't care what they are pushing or in which direction - it's possible to get the required speed with a 20 ton payload. The idea was never proposed because of numerous reasons (one of them not thinking it would yield a better understanding of how the Orion heat shield works - they thought it was perfectly fine to test their theory with a crew on board, and I applaud their confidence).

There never was a shield test like this. The only other crewed capsule in operation today has had a few uncrewed flights without incident before taking astronauts on board, under much more forgiving reentry profiles. I sincerely hope the Artemis II shield shows no chipping and is well within the expected behaviors according to their current understanding, but, then, again, Artemis III will carry a new design, with changes informed by the first Artemis flight (and near failure - it was uncomfortably close to burning through the hull). And it will have astronauts on board on its first flight.

Doing a shield study on the lines I proposed would be politically complicated for NASA and would undoubtedly serve as an argument to further cut funding to Orion, as it would show they don't trust their designs, or don't completely understand them. I would also delay the next launch, which is, again, a politically charged thing.

I trust their math, but there are incentives for cutting corners here. Both Challenger and Columbia were lost because people forgot they were experimental vehicles operating under conditions we don't fully understand. They were treated like 737s.