That could be at the same time true on average and not true for the specific case where the founders don't know each other all that well (and therefore don't trust each other much more than you'd trust a stranger). If you have stats on the latter case, I'd be curious to see them. If not, consider collecting the stats from this experiment.

Maybe people are "good by default" and all that, but I do have some very early stage startup experience (VPEng), and both the founders and the employees have enough trouble trying to not get screwed even without such additional complications. Money and egos always find a way to ruin everything.