In the traditional business, I suppose the answer would probably be yes (although I haven't really seen anything that supports this). Working in tech however, is much more of a crapshoot. Most of the time, you can't really research a market you're creating. This alone makes the whole process a giant guessing game.
If forming a business plan is just a series of guesses, you'd be better off moving straight into the part where you're actively testing those guesses with a workable product.