Time spent performing thesis research is accounted as course credit hours (There's typically an 800 or 900 level course for exactly this.) After all, you
must be "taking classes" every semester, with very limited exceptions, in order to even be enrolled in the program.
Moreover, in my field, RA work for an advisor should ideally coincide with your thesis work. So in that case, the main thing a PhD student does is two-for-one RA+thesis work. If it doesn't coincide, that's not a great situation to be in.
And I do understand what getting a PhD involves, as I have one.