I agree, but I was taking the work of translation to be entirely on the side of an AGI: it would take whatever sentences it thinks in a meta-language and translate them into human language. Figuring out how to express such thoughts in our language would be a challenging practical problem, but that's exactly where AGI shines. I'm assuming, obviously, that it wants to be understood. I am very ready to agree that an AGI attempting to be obscure to us will probably succeed.