I've spent quite some time today trying to find a way of wording this. I can't. I think he's an "censored".
There have been zero cases of MCAS operation in the USA. So, no better trained white men have saved the aircraft. Whist there are very likely inadequacies in the training of these crews, that exists everywhere. There have been plenty of comments of various forums about how 'I' could have saved the day. Until you are there, and faced with the issue, with the knowledge that was available at the time, you are touching something best left alone.
Yes, in one case the Captain turned the stab trim back on. I don't think that was a mistake. Sadly, he was in a situation in which that was his last chance. Because Boeing had never ensured that the manual trim had adequate authority, he actually needed the electric trim back on to have any chance of regaining control. I can see exactly what he was trying to do. Sadly it didn't work. His last thoughts would not have been about the quality of Boeing engineering.
Will it be the most tested aircraft ever. Probably, but not in the way implied. It probably already was, given that it dates back to the mid '60s, and has gone through many variants. The testing involved in fixing this mess is almost certainly trivia compared to what was done testing the initial FBW aircraft. So, no, it isn't the safest aircraft. It isn't even certifiable at all under the current regulations.