Skill level aside as push tests can convey various levels of skill --
We have, by numerous accounts, something that Ueshiba routinely did. ( http://www.aikiweb.com/forums/showthread.php?t=14991
We have something that Ueshiba thought well enough of that he allowed himself to be taped. Remember the incident with Ohba where Ohba attacked earnestly and Ueshiba was furious? ( http://www.aikidojournal.com/article?articleID=501
) Ueshiba seemingly only wanted to show specific things on demonstrations. It would appear push tests were in line with what Ueshiba wanted shown.
So, we have something which Ueshiba seemed to place some very high value on in that he did it quite often, was taped doing it, and very few could replicate. And those push tests *are* an indicator of "IT".
People can relegate push tests to some obscure corner if they want. They can rationalize them away. They can "replicate" them by not having the pusher use 100% effort. And they can completely ignore them. But, the fact is push tests were something Ueshiba valued.