Data Type > App Data record field displays "(error casting to string)"

I have a Relationship Data Type with Owner & Relation fields of Data Type Person.

When I create a record and view it in App Data, I see:

While of the same Person Type as Owner, the Relation Field displays “(error casting to string)”, and the Owner Field displays it’s email address (which does not exist in Person).

Why are these not both Unique IDs, why is Owner an email address and why the “(error casting to string)” error?

I do not have any Issues so I am worried about the impact to App functions (altho’ I will test thoroughly).

As is typical, I think I’ve “solved” this soon after posting.

It’s a artefact of App Data > Primary Display fields settings. Changing the Primary Display field of Person from User to Owner fixes the alleged issue.

Resulting in:

There the Data is OK and there shouldn’t be any issues with the App.