Change 132973 had a related patch set uploaded by Manybubbles:
Stop prefix: filter from searching redirects

https://gerrit.wikimedia.org/r/132973

Interestingly, the intitle filter does not seem to include redirects.

Looks like lsearchd doesn't include redirects with intitle as well:

https://en.wikipedia.org/wiki/Special:Search/intitle:%22quantum_mechanical%22
https://en.wikipedia.org/wiki/Special:Search/intitle:%22quantum_mechanical%22?srbackend=CirrusSearch

The reason prefix: includes redirects is because it "looks like" a prefix search, and prefix searches include them. It'll drop them when this is merged and released.

Change 132973 merged by jenkins-bot:
Stop prefix: filter from searching redirects

https://gerrit.wikimedia.org/r/132973