Or more accurately four of them wouldn’t have. Where before there had been one goth, one jock, one geek and one average guy, there were now four goths.
Of course only their clothing had changed, so Biff was still muscular and sported a crew cut and Jay still had short blond hair, and neither they nor Jon had gained any piercings. Then it clicked in their minds - that must be what was wrong! Obviously if it was normal for them to be dressed as goths, then they must be goths, and no self respecting goth would be built like a jock or leave his hair like Jay’s.