Use case

This can be seen on the SearchAnchor docs page. Remove some of the suggestions and you can see the extra space.
https://api.flutter.dev/flutter/material/SearchAnchor-class.html

This covers most of the screen and is not ideal

Proposal

Shrink wrap the suggestions material to the size of the suggestions