https://git.koha-community.org/Koha-community/Koha/src/commit/b0b168b6f84ef00babf566097933de7a338726a7/C4/Search.pm#L2136

Lines 2143-2144 still claim it returns a URL encoded value, though when bug 12071 stopped it from doing that, it did fix another mention of the URL encoded value

Lines 2148-2149 says that $matchpoints as a hash ref is bibliographic data from Biblio::GetBiblioData, but a hash ref $matchpoints can also be search data from an advanced search (and, not sure but it may very well be that even a simple keyword search passes a hash ref, since bug 11572 doesn't make much sense otherwise)

Lines 2151-2153 are either completely wrong if we no longer ever pass a scalar search term, or are wrong that we always return 'title' since we return either that or 'isbn' if we sniff out that it's an ISBN.