I think the confusion comes down to the difference of 'having seats assigned' and 'being able to select seats yourself'.
Any booking will have seats assigned and as far as I'm aware it's pretty much a random process (although two passengers on a booking should be seated together).
It then comes down to elite seniority as to when you can choose your seats if you're not happy with them. Golds/Silvers may choose at any time via MMB (manage my booking). Blues can choose/change at T-24.
So in answer to your last question - yes!