I'm confused, is this still flashback because at present they both have long hair???

Yes it’s still a flashback, hence the “few weeks earlier” at the start of the chapter. Hair can grow and be cut all the time. Hair especially grows back fast on dudes tbh

yes its still a flashback. the flashback parts are roughly sometime after they burned down that building in ch 11. and that flashback is a few years before the present where jihoon was stabbed (going by the length of gitae's hair, it has to be at least a couple of years between the past and the present)