I heard something similar, but with a slight twist - when any decision is to be made, make sure you have a prime number of deciders, otherwise there is the possibility of deadlock. I think that's from the founder of Sony? He had a lot of cool ideas like that.
Not too many companies have 9 founders, though, so I guess your version works well enough for startups.
Fair enough. But, in my experience, most issues that cause deadlock reduce to binary decisions - in which case having an odd number of deciders is sufficient.
If you have to account for n-ary decisions, then you can never be to guaranteed to be free from deadlock no matter how many deciders you have (trivially, consider the case where n equals the number of deciders).
Not too many companies have 9 founders, though, so I guess your version works well enough for startups.