When you tap one of those fields it bounces you to a contact card. If it is an existing contact (for example, yourself), you just get the full contact card. If that contact card has multiple addresses (my contact card lists ten), you get no indication of which one it was sent to.

At some point in time the actual email address used was flagged with a little “recent” badge - by itself a confusingly-worded tag - but even that doesn’t show up consistently.

It’s stupid because there’s really no reason to play hide and seek with the email address - that’s an identifier that people should generally be familiar with (since you have to use it reasonably often), and lots of people have multiple addresses that they can receive mail at.