Well my brain functions like this:
software has new dark theme >>> user chooses dark theme >>> users expects to see some kind of dark theme applied also to help files >>> user is disappointed to see that the software did not choose to open alternate version of help files >>> user does not check for their hypothetical existence so to not waste time
If you and more importantly Mr. @Florian do not follow that path of thought, then I will have to lobotomize my brain, so that it will maybe stop producing such logical expectations of aesthetic nature