Yes, I know that, and also the manual deals with it; the problem is - or was - that I didn't want to switch off MU (where I was) to switch over to the Lv setting, play with that yet again, and then switch once more to MU.
The manual, should you have it to hand, is less than crystal clear, and if I can remember from the shiny top of my head, one had to dig into a further section of it to complete the information process which I remember (willing to accept I could be mistaken) to be spread over two separate sections. You can't access Lv at all with Mirror Up - or at least, I can't. The switch has to be set either to Lv, or, alternatively, left on S and then the little Function button down below the iris stop-down button will bring it up when pressed. In either case, it requires that the camera be touched yet again after focussing, which I don't feel is clever policy. I do use an electronic release when possible, and that helps enormously - one of the best accessories.
So yes, it's good to have the Functions button capable of affecting the change over to Lv, but unfortunate that it still complicates the use of MU. I thought that Lv functioned after mirrors were out of the way, so I wouldn't have imagined that could have turned into a problem.