Lets go over some definitions..How are you not being Ignorant? you're asking about markings not appearing on Darui knowing that Sakura didn't have the seal yet.
It has been used Twice First by Tsunade then by Sakura onoki was clothed, Obito wasn't.
Ignorant - lacking knowledge or awareness in general; uneducated or unsophisticated.
Have you seen the seals marking expanded onto another person while it was active? No you haven't. Oonki was clothed, yes. But how do we know the markings did show up?
Possibly - (1) perhaps (used to indicate doubt or hesitancy). (2)in accordance with what is likely or achievable, in particular.
Reread the tittle of the thread, then go back an reread the end posting.. Could another person (Not The Seals User) be regenerated using this same method.