I'll leave this up for debate, but basically for me, I do think it's a real thing, but I'm always more skeptical of such claims because bisexuality can be used as a middle grounds sort of thing for people who can't decide (<--- lol at that word), and often come from people who very often aren't even bi by the definition of the label.
As a guy who was searching for a partner before I found tru luv (cause im young and stupid lol), this was a problem for me.