The search field you get when the autofill can't identify what logins pertain to an app seems to search for each character individually, instead of searching for the characters in the order you type them. This makes it virtually impossible to find anything you're looking for, and is contrary to how search works anywhere else in the app.
In the example screenshot below, I'm trying to find the "Eventbrite" login, and you can see search is matching every single result that has any of the characters anywhere in their title, instead of giving me the one I'm actually looking for.
1Password Version: 7.2.1
Extension Version: Not Provided
OS Version: iOS 12
Sync Type: 1Password