Hey khyber'

I have found with seedlings in soil or soiless mix, that after the first week of 24/0 they do better after that in making more roots using 18/6.

Tho I have found in the clonners, cuts root faster at 24/0, then 18/6 or 12/12. Depending on strains they start to show in 3-10 days.
I have not found personally or in any plant literature evidence of root growth during the dark phase.
OM