mneah
I think it could help you learn how to putt up a hill into a cup and with alignment.
I dont see how it helps with distance control.

Your brain uses depth perception from your two eyes to figure out how far away something is, trying to translate a short uphill slope (a severe uphill slope in some cases) into a long slight slope is too hard and wont have good results (I think)

Better to use a sheet of cardboard with a "hole" sized slot cut out of it.
(Kinda like a squared off C shape)
Too hard and it will pass right through, just right and it will stay "in"