there is a difference, and youre right, its subtle. subtle enough thtat at this level of discussion, with the context provided, no one could mistake your meaning either way.

since you seem to be curious, “convinced of” refers definitely to being fully persuaded by the relevant subject. look up the dictionary definition of “of” and youll find a bunch of use cases, many of which particularize or otherwise specify something that follows.

“convinced about” is still definite about the conviction, but the word about makes the subject of conviction connotatively less particular. about means something approximate, similar (or perhaps similar enough), or nearby. otoh, it has a perfecty valid use, as in the case in which you used it just now, as a specifying preposition.

They both work, theyre both grammar. “not sure about” is more common than “not sure of”. “not convinced of” is more common than “not convinced about”. i leave it as an exercise to the reader to puzzle out why that might be.