Well, it's one of two things...
Either:
1.) Keep the anti-spam actively scanning posts, possibly getting false positives.. even though it will keep a lot of spam out
or
2.) Just go back to the old way, allow a lot more spam, and allow it stay on the forum longer until it's found/reported.
:imho: the anti-spam sending spam posts (even w/potential false positives) to moderation is less work than finding & deleting spam posts/responding to reported spam posts/etc. Moderated posts are kept in a central location, while spam can be all over the forum.