Isn't it equally misinformation to say that an MCB isn't fine for isolation without knowing the circumstances?!
In my world it doesn't seem totally ridiculous to suggest that
a) you might turn a circuit off before you work on it
b) you might not expect there to be two supplies
c) it would be better if you only had to turn one circuit off.
That's the point, surely?! We both know and understand that MCB's are often single pole, and the principles of isolation. I think that labouring this only distracts from the point I was trying to make.
Granted, if we just threw the double pole main switch my point become irrelevant but in the real world circuits often get worked on with other circuits live.