Yes, the sig banner has to update itself from the site that hosts it. And that same site has to get the stats from Bungie.net. If it doesn't update for a prolonged period of time, best to let the site owners know about it.
I saw someone's the other day who had a 0.00 W/L and ZERO betrayals with almost 1500 games played. I don't know if it's even possible to have no betrayals with that many games played. So yeah, it's probably just a little glitch on the website. Maybe you
can report the problem to the website and they can look into fixing it.