Great in theory, but you cannot drive like that. How do you want to drive around there to try and do a 15.0 while with just a little twitch before a corner you do a 15.3 and you're out. They don't know the time of their lap, and it's not like they've plenty of laps to figure this out; just 1 or 2 and then they come in again. There is no time to risk anything as it seriously affects your race here.
Rest isn't true either, at most tracks this year we've seen similar gaps between Q2 and Q3. See Bahrain, Sepang, Melbourne.
I don't understand why this is so hard to believe. The ones who are most comfortable with their speed are naturally going to drive within themselves in Q2 so that they don't
make a needless mistake. Hamilton did half the number of laps of JB in Q2, if he needed to he would have had plenty of time to go out and do another run. He said after qualifying:
"You go out in Q1 and you don't push 100%, here particularly, Q2 a little bit more, and Q3 then you're flat out, just everything you've got, even if it means you're going to crash, you've just got to take every little risk you can to get that one millisecond."
The circuit i'm sure improved a bit, but it didn't suddenly improve the 6-7 tenths over the 5 minute interval that Hamilton, Webber, Schumacher, Rosberg and Grosjean all found. The cars that were logically slower (Ferrari, Williams) barely found any time at all in Q3 over Q2 - suggesting they were already maxing out their potential in Q2. It's obvious the big guns were keeping their powder dry until the final session.