Hard to mistake two users using the same IP.. obviously why would he admit it even to someone close? Maybe it was a really embarrassing account or one that may get him ridiculed nonstop. I don't think that account was his though, the likes and posting styles of that account seem to not be consistent with him.
Like I said earlier, it's easy to act like someone else when you're anonymous online. That said, it could potentially be his mate's account that was coincidentally created and used at JG's place or whatever.