I wrote “if the animations are simply distorted, you may be able to fix this by” because I’m not sure what the cause of the distorted animations is for sure in those instances, since I’ve tested the tutorials on retargetting ASP animations to the Mixamo S.W.A.T character and they worked without a hitch. If you will describe to me which specific characters you are having problems retargetting, I will see if I can resolve the issue or I will submit an official feature request for an automatic T-Pose as you have suggested.
Thanks for the feedback.