Evohome: Should Optimize have an immediate effect?

I enabled Optimize a few days ago, and I assumed it works like my old Honeywell stat, where instead of the heating coming on at set time (say 8:00), it would come on as early as needed, to get the house to temperature by that time..

The first schedule I have is at 7:30 and I am used to waking up to the sound of the TRVs doing their whirring at that time.. But I assumed that because I had enabled Optimize, this would all happen a bit earlier.

But it didnt.. The system still started at 7:30..

As I understand it, if you have a 7:30 start at 23 degrees, with Optimize off, the boiler will start at 7:30 and run until the room/house hits 23 degrees.. But with Optimise on and the same Schedule, say the house got down to 17 overnight, the heating might come on at 6:45, so that it it 23 degrees at 7:30.

Is my understanding of Optimize correct? And if so, why didn't it work? Perhaps it takes some time to "Learn" the house and its dynamics?

I did notice that 2 (out of 12) zones had a zig zag arrow icon, which according to the manual means Optimization set.. But it didn't have any effect? The heating still came on at the set point and not before... And why only 2 zones?

Can anyone shed any light on this?

Jon