If I had to guess, I think the minimum length=2 was done to avoid slow query performance on large vaults (probably targeting languages like English).
Code:
It probably makes sense to support this for languages like Chinese.
Whether the behavior should also be changed for languages like English would probably depend on performance (making sure there is no lag when a user types 1 character → 2 characters → …) tested on a very large vault.
I think a possible workaround in mean time is to add a wildcard asterisk * to your search query. I haven’t actively tried this out, so I cannot guarantee it will work.
This isn’t exactly the same query since it changes the search behavior in fields like Notes (the default is exact match while asterisk adds partial matches).
e.g. 桥*