Thats a stupid analogy comparing mallet an blade putters to this issue. A player swings both a mallet or blade putter. With this a player is actually groind the end of his club to his belly area to stabilize it. It is not a free swing.
Second, half you people in here need some basic HS level instruction in Logic. Just because someone has not won a major with it or it has not taken over the game does not mean it fails to give one an advantage. The real data is to look at the putting stats of players who use it before they adopted it and after. A highschooler with a reasonable IQ would know that.
If all the ohr clubs in the bag are limited to 48 inches, the putter should be as well. Whats next, a putter shaped like a Y and at the end of each of the top Y legs you have a curved bar which you hang over your shoulders? That would e accomplishing basically the same thing as a belly putter, using other parts of the body other than thebhands to rest and stabilize the club against. Would you Pro belly putter fanatics be ok with such a Y shaped club, and if not why are you ok with a belly putter which basically does the same thing???