My own opinion is - beside the question of what use such information could be, and how much it can be open for abuse, there is the fundamental issue here of privacy and basic respect for another person.
For example, I don't have to go around telling people you are a Buddhist or a master cat groomer, and that type of information is not really relevant to anyone else, nor is it necessarily appropriate.
It is the same here.
I would be careful about the guiding categories offered in the texts, and that it is better or perhaps easier to maintain some normalcy in how you view people and their lives.
There are enough Buddhist Masters across the lineages for there to be some guidance across the tradition. And in my own opinion practice is far more fruitful than conjecture about any person's understanding, or lack thereof. The texts are complete.