What do you think? (Yeast Volume vs. Fermentation Duration)

If you decide to make a "half batch" (2.5 gallons) and you purchase a nominal test tube of WL yeast and pitch it, that you have essentially doubled the yeast cell count and thusly reduced the estimated primary fermentation time that is stated on a recipe by half?

I did this last week (and No, I don't have a hydrometer yet. Working on it though) and pitched the whole vial on a partial grain\extract recipe. All of my other batches that were "taylored" to the 2.5 gallon mark (including dry yeast packs) fermented in excess of five days or longer. This batch fermented approximately half of the time stated on the recipe ( 7-8 days for a sweet stout)

Does this sound theoretically correct?? More yeast, less wort, less fermentation time?

Thanks for any insight..

Larry

Less wort is the real key, since the yeast growth period is typically shorter than the fermentation period.