I don’t know if this is meant to be sarcastic or not, but manbuns are a very modern hairstyle that only date back to around 2012. There were topknots, but those look different and wouldn’t have extra hair hanging down the back. Also they’re (topknots, not manbuns) more of an Asian or Polynesian thing, not typically something you’d see on a random British teenager circa 2004 (given he’s not a harpy and hasn’t started the band yet so it can’t be the future).

Like there were presumably some people with manbuns before the style hit the mainstream, but almost a decade before just seems anachronistic. Imagine someone running around with a big modern style gelled up mohawk in the 50s. It doesn’t immediately seem like it would be out of place, people back then shaved their heads and gelled up their hair all the time back then, right? And the historical hairdo it’s based on, the signature hair of the Mohawk tribe did exist (though ironically it was actually closer to what’s now called a fauxhawk) but in spite of that it just… didn’t exist, people just didn’t partially shave their heads. And similarly, even though it’s never been that rare for some men to wear their hair long, putting it up like that just wasn’t something that people did. It might seem strange to consider from a position over a decade on from the style coming into existance, but it’s true.

Have a Wikipedia for some proof: https://en.wikipedia.org/wiki/Bun_(hairstyle)#Man_bun