I would say that creating "flowers" in non MJ plants then yes, rootbound plants do tend to throw out more flowers. For example, the Mothering Tongue variety of plant, more commonly flowers when it is rootbound. As do Jasmine plants. I generally think this is done to make flowers attractive to customers going into garden centres. People will tend to buy the plants with lovely blooms already on them, not actually realising that when they get home the bloooms will not last that long.
When dealing with FRUIT, which I would class the flowers of MJ more in line with, then rootbound means less fruit in my opinion.