>It's not only the AND approach. You do not allow it at all unless contained already in a phrase.

The AND approach is the default mode. The only one is the exact match.

>What about the 2nd half of my post where I asked why this is? Performance? Arbitrary? Seems like changing a 3 to a 2 wouldn't be too tough. I understand why you might not want a search on 1 character as you would get almost 100% of the messages, but 2 seems reasonable.

There's no specific reason. As I said, it is not supported because it's not implemented.