Do the 3g buckets next time. If the roots were a complete wall around the rootball, then they had plenty of extra root growth possible in a 3g bucket.
And yes they will be bigger.
I've never heard a gallon per anything, every plant grows different, some grow tall with deep skinny root systems, and some grow short and stout with a wide vigorous root ball.
I transplant when 'ready'.
Ahhh I've got between 2-3 weeks left, and so does your next G'O'Matic round, sounds like we'll have almost the same harvest day!