Ok, so Byakugō instantly starts to recover the wound but the wound takes a few seconds to repair. That's all, the wound doesn't instantly close up, it takes time but the activation is instant.You cannot make up your own facts or add to a facts
"When ones life is effected by grave wounds pushed to the point where they'd normally die, ones body is instantly returned to an unwounded condition.(Instant regeneration)"
How man times do I have to post facts?