Ye I don't know tbh.

What I do know is that my plant #4 from seed always raced ahead and in its stretch period insanelly did so. Even if it was 4 inches from the 600W it raced 1½-2 inches a day.
They all gre a lot during this period but every other day plant 4 grew one inch more than the others so 10 days into the stretch period it was 10-12 inches taller than the next one and got slammed with a serious emergency break. Broke it's spine 3 times now hehe. It still grows hard but has slowed down a bit and the Z shape it is growing in also helped to keep height down.

As for the clones it's interesting. I will surelly keep a close eye on it when I do my next grow from clones with the same genetics.
A clones birth age is the age of its mother so in my case my clones started as 28 days old from seed. The plants I took the clones from were growing hard then but it was a few days before the stretch period started for real so in theory the clones should start growing hard as soon as they rooted. Can't say that they have so that sugests that your theory stands.
This might cause me to reconcider alltogether actually.
My plan was to more or less discard plant 4 clones even though that plant shows excellent signs of becoming a top yeilder on the basis of it being too unmanagable o grow indoors. I am leaning to plant 5 clones for mothers and I still do as it is a beautiful plant with a LOT of flowering and close between nodes. Plant 4 (the stretchy one) was fastest to start flowering and is building on hard though and from what we seem to have discovered here just might be in the race still now then.

Nice discussion by the way, thanks for picking up on it and coming with very valuable input.

Puffzter