I don’t quite understand the fascination with a three-AOA concept. The questioner seems to imply that the computers need to know which AOA signal is correct. They don’t. They only need to know that one of them is wrong, which means that the MCAS routine should not be employed.
Still, Boeing went a step further with an internal algorithm that functions as part of the comparator. To me, this is the very synthetic value that the questioners are asking for. And still it is not used to determine which one is wrong. Just that one of them is wrong, and MCAS should not be activated.