It's about time I gave the secret. At 1.00 Power, unfocusing gives you 2 frogs, focusing gives you 1. At 2.00 Power, unfocusing gives you 4 frogs, focusing gives you 2. At 3.00 Power, unfocusing gives you 4 frogs(?), focusing gives you 3 frogs. At 4.00 Power, unfocusing gives you 4 frogs, focusing gives you 6 (4 front, 2 side / diagonal).
I don't think this is the reason unfocused does more. My argument is that, while you do get 4 frogs at 2.00 power, you can only shotgun with 2 of them hitting anyway, but it still does much more damage that hitting with the 2 focused frogs. Here's my theory:
As with previous games, a character's normal shot (amulets, christmas trees, whatever the fuck Sanae uses...) are strongest at 1.00 power, and reduce in strength as you gain power. However, in SA, there were exceptions to this rule: namely, Patch-Wood and Patch-Earth. I believe Unfocused SanaeB (as well as MarisaB focused or unfocused) is also an exception, so the path goes like this (in order of unfocused then focused):
1.00 power
Powerful normal shot and 2 frogs hitting
Powerful normal shot and 1 frog hitting
2.00 power
Powerful normal shot and 2 frogs hitting
Weaker normal shot and 2 frogs hitting
3.00
Powerful normal shot and 3 frogs hitting
Even weaker normal shot and 3 frogs hitting
4.00
Powerful normal shot and 2 frogs hitting
Weakest normal shot and 6 frogs hitting
Now, based on this theory, I have to assume that frogs themselves get stronger, otherwise Unfocused 2.00 is the same as (or better than) Unfocused 4.00 power. But this is just speculation.