But those sentences are also perfectly meaningful assuming the other sense of "satisfied", which may be what GP meant. Ie. "I am convinced that you did your best" and "I am convinced that it contains no gluten".
It's not that hard to draw it: 'I am satisfied that this man is the one who killed my dog'. Whether you are convinced that this is the man, or whether you are pleased that this particular man killed your dog are clearly different senses.
But would you not be pleased to be certain who killed your dog? It's not a 1:1 concept mapping, but the conceptual space is close enough that the semantic drift of "satisfied" is completely understandable.
