Statistic shows that people sometimes use query syntax on Wikidata, such as:
- query -with -minuses
- "quoted string" search
etc. New search does not support this (at least yet), and these are pretty rare (less than 1% of queries) but they do exist. So we may want to fall back to old search when we detect such request - despite old search being generally bad, it may return at least something for these queries.