Silvio Mecucci wrote:
The problem is that if I, as a flight instructor, say to someone
"Never use
it in this way." and that someone asks me "Why ?"

And the reply is, because if you do that, then you are being a test
pilot.
At any rate, I would certainly not be willing to find out if it works.
But if you really need to know, can't you just look at the fuel system
diagram in the POH?