@Seaweebrainz
Just gonna debunk something right here and now: There IS no official wiki. Both TM Wiki and the various FGO wikis are edited by volunteers and, considering the amount of content, very frequently filled with inaccuracies. So every time you argue about something using the wiki, make sure you have source of the quote ready at hand.
Which in this scenario, is remarkably easy to find, anyway. Fate/Grand Order, Okita's Bond 3 Biography:
Mumyou Sandanzuki (Lightless, Three-stage Thrust)
Anti-Unit Mystic Sword. Maximum Targets: 1 person.
The sure-kill mystic sword of Okita Souji, a rare genius swordsman.
Within the "first thrust", a "second thrust" and "third thrust" are contained.
Not "almost simultaneously", but horizontal thrusts that are released "exactly at the same time" from the hiraseigan-no-kamae; a secret sword technique produced by transcendental finesse and speed."