FCC do have trains put on platforms 0-5 throughout the day and even into the evening, but with the work being done on the platforms it's a mess and can change last minute. I can usually see the 'booked' platform but I'd say that I am probably wrong about 50% of the time at the moment so it's really not worth looking to get a heads-up on people waiting on the concourse or by 9-11. Thus, I wouldn't read into the situation of where FCC trains are going and why they're not behind the gates.
Bear in mind the plan will be for ALL platforms to be gated, and it sounds like 0-5 is some sort of experiment at the moment if it turns out that anything will open the gates! We all know that staff can easily be persuaded to let you pass by showing them anything orange or gold in colour, but for the gates to do the same seems rather bizarre!
Perhaps after they've done this little experiment, they should just leave them open until the next phase of development - which would then allow FCC to take staff back to 'protect' stations like Potters Bar that have been empty for weeks as a result of them being relocated.
I can see for today that a number of trains are due to go to Cambridge, Peterborough or King's Lynn from platforms 1, 2 and 3 - and a couple from platform 8. All the others are 9, 10 or 11.
Now whether they run from those platforms is another matter, but it seems that FCC is trying hard to schedule services from only gated platforms.