You can, I’ve done this a few times.
You can leave plants vegging besides auto’s in flower, but i should mention it does get tricky balancing a proper Rh% for both veg and flower. Plus, when photoperiods (if that’s what they are) Switch to flower, they need that 12/12 light/dark period to induce that, So they will need to be moved away from the auto -if that’s what it is- eventually.
(Just my thoughts)