only if too dense or one is "strangling" the other and hoarding resources. (via available opportunity, nothing malicious, lol)
roots intertwine outside.. in some other growing methods indoors too with no problems... as long they aren't cannibalizing each other should be fine. if you see symptoms that make no sense, like being rootbound, consider a larger recipticle or less vege time.
as long as rootball and most of mass is compartmentalized, i don't think they'lll cause trouble for each other.