I submit a theory to you: "Jedi trainee hair" or anything aside from some variant on "thin single braid on the right side" actually isn't standard or required or anything, it's just how Obi-Wan was wearing his hair that week. (possibly most of it got burned in a mission gone wrong and Qui-Gon cut the singed parts off but left bits of it long, /probably/ accidentally but he won't admit that, and Obi-Wan just ties it back in a nerf tail because he has a weird sense of humor.) (part 2 to follow)
part 2: anyway then when Anakin becomes Obi-Wan’s padawan Obi-Wan gives him a braid and says “there, the rest of your clothing and hairstyle is yours to choose within reasonable limits, please stick to some variant on Jedi robes but there’s a very large range of options—” and bb!anakin’s just like “…exactly like yours. DECISION MADE” and so this tiny nerftail thing just gets. immortalized.
Ohhhhh my GOSH BABY ANAKIN PICKING JEDI TRAINEE HAIR BECAUSE LOVE. I mean, I’d buy it: remember how much he worships Obi-Wan in the comics?
Congratulations: you’ve discovered a headcanon for Jedi Trainee Hair that I…can almost live with (even though in this version of events Obi-Wan got stuck with the hairstyle initially by accident, and then kept it just to be weird, hahaha, which in fairness, I also kind of buy.) That is one hell of an accomplishment.