If Odo's appearance really was typical of the Founders, it seems like the Vorta (Erris, Emmis, maybe?) from the Season 2 finale should have recognized him as one of her gods. Instead, she barely acknowledges him when he steps up to arrest her before she escapes.
Eris was trying to be undercover. Though her cover was blown, she was hardly around long enough to give away anything she knew about the Founders and the Dominion. Not to mention that it is unlikely that every
Vorta interacts directly with the Founders. It's entirely possible she
had never seen a Founder herself, and wouldn't be able to peg Odo as one.