I'm not sure where that info comes from, I've seen it mentioned a few times here and there, but my last read a rep stated nothing has changed.
I just had a small bit of bry in my new tank a couple months ago, took about 2 weeks of using Tech M and it was gone.
Mag is fairly safe to elevate, but I'm not going to say do other than what directions suggest, that's up to you, others may chime in on that one.