I don’t think it is an upgrade TO LE because that is the “lowest” versions (LE/AI). Are you sure you read that correctly?
The other possibility is that, you used to have an LE or AI license that was included with some hardware and then you subsequently upgraded that to Elements via some discounted offer. So now, perhaps, you have an Elements license (which the free update is not for, according to MY e-mail) and no longer have an AI/LE license to update from.
At any rate, the only way to know is to post EXACTLY what the e-mail says and EXACTLY what license you have.
Otherwise, it is all just guessing.