Setting that var sets FR_AUTOREVIEW_CREATION. If $wgFlaggedRevsAutoReview === true as well, then it's like FR_AUTOREVIEW_CREATION_AND_CHANGES. $wgFlaggedRevsAutoReview is best configured as a bitfield but the old ways still work.
Thanks - I planned to set in the config
$wgFlaggedRevsAutoReview = FR_AUTOREVIEW_CREATION_AND_CHANGES;
So that just folks with the autoreview permission (plus editors, reviewers, admins, etc...) could have their edits and page creations automatically marked as sighted.