You know, I never really got why Vergil's Teleports have active frames.
Pretty much every teleport in the game is in the ballpark of 30 frames of startup and recovery combined with a few exceptions(Dante being the fastest at 22 frames followed by Strange and Deadpool at 25 frames). The only real difference between them is how they move and the ratio to startup and recovery making them harder or easier to see coming(Deadpool's are 100% startup, making them pretty much unpunishable but easy to see coming, whereas Phoenix has a 10 frame startup and is harder to block).
Vergil and Jill have active frames during which they are invincible. I don't really get it. Are they more like Akuma, and are physically sliding instead of teleporting? But Akuma doesn't even have active frames on his. Neither does Rocket Raccoon. Meh, maybe it's just the time they're not on screen.