Greetings!

I think this is designed to work that way.

I agree that it was probably not intended to be selectable, but I disagree with that feature (unless there is a really good reason behind it). There should be no reason that two of the search functions are limited, while the others are not. Even if there was no UI to change it, it should still default to whatever was set for the other search functions.

a "Mode=Insert" indicator could be up on the screen at the same time

Hmm... Depends on implementation. Given that the PIN and Year boxes are pop-ups, overlaying the existing screen text or visual, I do not know if they would be able to do that without rewriting that UI section completely.

a level of self-documenting user instruction . . . I like this idea

I do too. My concern is that it might be a more significant UI change, and unlikely to happen in the imminent future. I fear that this falls into the "that's not a bug, that's a feature" category. At least for the documentation and selection part. I still feel it is a bug from the standpoint of not matching the current select mode used in the other searchs.