While I can feel your frustration and agree that the big fat red warning might be better to talk about experimental rather than beta feature and suggest more strongly that there are bugs, it would seem that there it is a note that this isn’t ready for production.
The unfortunate truth is that new code is susceptible to bugs and there are many functions that have to be checked for necessary adjustments. Because it can happen that backwards are not implemented in a way that does not work well with complex numbers, there has been an effort to disable unchecked backwards on complex by default, and re-enable them after checking, so you might get more pertinent error messages.
If its any comfort, I might be able to get you a discount for the next PyTorch version, PyTorch 1.7, to be released this month.
Best regards
Thomas