up until recently I was always transplanting from 1/2 - 1 gallon straight into 7 gallons and flip the light the same day, some plants would grow super big anyway... I think if everything is right and the soil is healthy, the plants dont spend energy growing roots, growing roots gives them energy. no? But anyway transplanting a week or 2 prior to flip actually seem to increase yield so that's what i do now.
That said my very best plants so far were all grown 12/12 from seed by having the seedlings in the 7 gals container ... but it is not the most efficient way to grow because the room is always half full and a 7 gals container for a seedling increase the humidity of the room quite a bit for a baby plant.