well, what made me say that is. When i grew auto assasin, i germed them right in a 2 gal grow bag. They took ALOT longer to show sex and start flowering, than i was used to. I usually sex them in cups then transplant. Since these were suposed to be fem seeds i thought id get all females so wasn't worried about wasting dirt.
I have it in the back of my head that maybe when the roots get to a certain size relative to plant matter, a hormone or some thing is produced that induces the flowering. Maybe this is all tied some how to the roots.
Hydro AF's always get bigger and seem to veg longer before they flower. Even you stated you seen massive root growth. My AA's that i speak of also had ALOT of roots, the whole mass of dirt was basically roots. I really had to break them up when i composted the soil.
This is nothing i have proven, just some things i have noticed in my AF travels. The trigger for flower intrigues me, so i notice small things that have affected my AF's. Maybe flowering is delayed by letting the roots have as much room as you can give them.
Don't know if this applies to the dwarf phenos... They are the same in cups or big bags, for me anyways.
It's a tricky thing..