Ok, I stand corrected in that this is the way it used to work and how it was meant to be used even though there’s no mention of this functionality in the manual (not v3.0 nor v4.0) where it’s not stated anything about what happens when you turn off all the lights on the MW AT button.
I don’t know if they silently changed the behavior in a patch (I haven’t been able to find any patch notes mentioning this), or if it’s a newly introduced bug. I think that it should work the way it works now, with the LFO2 being always on when all lights are unlit (from the linked thread above, at least a couple of people seems to be agreeing with me), but it’s still super confusing when it isn’t properly documented (and it’s not the first issue that’s poorly or even flat out wrong documented).