Not my experience...and the aikikai is not a monolith, either.
It would be interesting to compare the failure rates of dan test in various organizations. For example, the failure rate (in 2005) of the ZNKR 8-dan exam that I mentioned earlier was 99.1% (12 applicants passed out of 1357 -- keep in mind the requirement to test for 8-dan is having been 7-dan for at least 10 years). My guess would be that in the USAF the failure rate over the last several years for 1- through 3-dan (these are the only dan ranks for which they test) would be close to zero. In fact, I wouldn't be surprised if it is exactly zero, though I would be very surprised if it was even as high as 5%. I would also guess that the ASU numbers are similar, though I don't expect either of these groups (or any other aikido groups) to release that kind of information. Of course, anyone who knows for sure or cares to speculate about their own organization is welcome to do so.
Anyway, the failure rate of dan tests is not the only issue I mentioned. Although increasing the possiblity of failure would also increase the pressure and create more adverse consequences for a bad performance, I still don't think it would come close to what you would experience in a real fight as long as we are talking about the the extremely compliant ukemi that is typical in most organizations. If you let people start to really attack then maybe you might have the beginnings of something useful.