No, actually, it's a statistically demonstrable fact. I don't have the data ATM but I can easily get it when I get home.
However it's got nothing to do with "several receivers in different areas" but rather with QBs accuracy, which decreases by length, and coverage, which is usually easier in shorter passes (cuts allow for more separation, and middle-of-the-field routes can put the receiver against LBs).
I think, however, that you shouldn't consider just the percentages of the playcall (as it might be - it could just be a read by Henne, but whatever). You should consider the percentages of the pass AND the percentages of the resulting field goal.
Say we advance 15 yards. It's higher percentage, yes, but we also face a 51 yard figgie - if you remember, Carpenter missed a figgie just as long earlier in the game. The probability of making that field goal are small.
If we advance 30 yards, it's now a 36 yarder - much better odds.
If we assign arbitrary odds to the plays:
Long completion: 30%
Short completion(s) for 15 yards: 80%
Long figgie: 30%
Short figgie: 90%
It's slightly better, odds wise, to go for the long ball.
Assign probabilities as you see fit, or wait until I get the data