If the tree always expanded when you typed, it would expand to a match, then when you type more and that node no longer matches, the tree would be expanded to the node that no longer matches. Maybe it could remember the nodes it expanded and collapse them again, but even then using text search would change your tree expansion all around. I don't think that makes sense when Text search filters
is unchecked. When checked, it might make sense because the only nodes being shown are those that match.
I gave it a try when Text search filters
is checked and it seems pretty OK, though it does expand a lot of nodes. Often times that doesn't matter, as the tree tends to get a lot of nodes expanded, but we'll see if we can improve that by remember the previous node expansion as you type.
OK, it is in 3.8.60 and remembers the previously expanded nodes so text search doesn't inadvertently expand most of the tree. We should keep an eye on this behavior during practical usage to make ensure it's a good solution.