I dont think 5 to 10 days dif on one grow is enough to draw any conclusions. Too many other factors come into play.
I ran white russian 3 times in a row in the exact same conditions and and each run finished at different times. I attribute that to inconsistency in outside weather making sublte changes in the grow room ( i pipe in fresh outside air causing temp and humidity fluctuations for example; also decreasing light intensity due to bulb wear and so on). Also, inconsistency in PPM strength, timing of feedings 3tc etc etc. And... even though they were the same strain, not every clone/seed is equal...
So who knows?