Reducing day length suddenly will induce flowering.
A friend brought me several clones that were under 18/6. I put them in a greenhouse and are now blooming.
They'll revert and get large by Autumn.
If you want a seamless transition from indoor to outdoor, keep your clones under 13.5/10.5 from day one. That means the Mother is under 13.5/10.5, as well.
And then put them outside when the outdoor day length matches the indoor.
I don't stress over a few flowers, or even some chunky buds because once revegged, most plants EXPLODE in size.
There are three plants visible in my signature pic.
All three were revegged after producing a seed crop.
Click on it, and you'll see how I do things.