I know what you mean, and it can be a bit confusing, but it's technically not 100% a bug, it's by design. Also, what you describe is not correct, actually. However, what you probably observed (without realizing it) is that if first set the cut-off, and then change the basis set, then the cut-off gets reset to 75 H. This is partly on purpose, we attempt to prevent the user from using a too low cut-off, but on the other hand it is indeed a (known) bug that if you set it to higher than 75, it is still set to 75. However, if you first select the basis set, and then the cut-off you can perfectly well change the density mesh cut-off on both the Basic and Numerical accuracy parameters tabs.