I don't know. This seems common sense but it could be a cliché too.
If we look at other domains, it is not always true. For instance, if you write novels that are not tied to some evanescent trend like a pop star's private life, then the chance of getting off the ground if not directly linked to the timing of publication. It would be the same if you are creating a newly designed chair.
Even on the web, let's take two success stories: when Wikipedia or Twitter were created and made public, I don't remember seeing five other contenders running behind them, and being only two-features-months behind. Same with, say, Minecraft.
I am all for quick development, because it is more fun, but not because it would magically increase to probability of success, which is too low to compute and unpredictable anyway.
I am also all for choosing carefully which path you take, especially when you cross virgin territories. You don't want to find yourself spending a night half naked with a toothpick for your sole defense in Borneo's jungle.