In 3.5, they're 10 intelligent. They're only 5 intelligent in 5e, though. Can't find any stats for 4e mimics, but I interpolate that they'd be roughly 8.3 intelligent.
I give even odds she expects them to fail and just wants to be in a position where she can stop anyone from breaking the Gate.
More to the point: Belkar has the wisdom of a short-sighted lemming, and only slightly more intelligence. Even if he was trying to give good advice, why would you expect him to succeed?
He's casually slipped in references to 4e/5e mechanics as those games came out, but he hasn't made many explicit rules jokes since the days when he was first toying with the idea of character development.
I dunno about the dictionary, but when I've heard people use the word, it's been closer to "amused" than "confused".
Belkar has ranks in two skills: Profession (gourmet chef) and Knowledge (prank-worthy trivia).