I agree that there are several factors that play a roll in developing white caps, but if you look at all the youtube videos on speed sailing, there are plenty of white caps in the speed canals that pop up with only a couple of meters of fetch. The canals are filled with caps. Exactly my point in my first post. Wavelets can cap even if only a few centimeters high.
The video below is an example. While this isn't a canal, it shows how little fetch is necessary for caps to form if there is enough wind. However, I doubt that there would be caps along the shoreline if the wind was 10 knots, but they will form, the only question is how much fetch is necessary to create caps in 10 knots.