What I quite rightly said, is monitoring VHF 2 is a line of defence against a VHF1 failure. That is good airmanship.
If my box 1 fails, instead of every 3 minutes when I haven't heard a call (common over for instance the North Sea) asking for a radio check, if ATC can't make contact with me, for instance for a heading change, they will call a few times and then make a call on guard, something I will immediately hear, and very shortly after diagnose a VHF 1 failure.
All well and good, but what if it's your VHF 2 that has failed?
When would you instigate the call that you've said that you wouldn't make?