As you can see in the screenshot below, I'm able to click the Sign Up button and the button isn't disabled in the DOM snapshot, but according to the Command Log output, the button element has the disabled attribute. Why is that?
If you want to reproduce it, check out this commit to my RWA fork.

Update:
Adding assertions didn't affect the results, but FWIW, I did notice that the element in the second assertion message doesn't have the Mui-disabled class while the element output to the Console does.
