Interesting stuff. I know that my own unscientific experience lately shows that sticking to those precise numbers suggested by yeast calculators is not necessary. To me its not as much about how many billion cells as it is how healthy and fresh they are. I haven't tried pitching a vial, haven't used white labs at all. I suspect that if they used wyeast in this test, smacking the pack and letting it come to life and inflate, that the results would be even tighter.
Lately I've been doing my starters without stir plate, highly oxygenated 2 quarts in a gallon jug, crashed after high krausen and decanted. No concern for cell count. Great results. Im sticking with that.
But, I suspect that pitching a tube or smack pack into 1L of wort at the beginning of the brew day, and pitching the whole thing into the finished wort would produce decent results. Unless the yeast was so old that it didnt have some activity by then. On that note, age/viability of the yeast is another major factor in a no starter pitch.