Bug 73321[1] pointed out that generator=search was incorrectly trying to set the same "searchinfo" and other properties on the result that were set by list=search.
Gerrit change 172794[2] removes this setting, so generator=search will no longer provide 'searchinfo' or 'interwikisearchinfo' members in the result. Interwiki titles from the generator will no longer populate an 'interwikisearch' result property, but will instead be included in the generated titles and thus (for action=query) will populate the 'interwiki' property.
This change should be deployed to WMF wikis with 1.25wmf9, see https://www.mediawiki.org/wiki/MediaWiki_1.25/Roadmap for the schedule.
[1]: https://bugzilla.wikimedia.org/show_bug.cgi?id=73321 [2]: https://gerrit.wikimedia.org/r/#/c/172794/