Discovered items (LLD) not passed through the filter but doesn't deleted yet, still continue to be monitored.

Created based on comments (9) from ZBX-3286

If some item not passed through the filter but doesn't deleted yet, it still continue to be monitored:

mysql> select i.lastclock, d.lastcheck from items i, item_discovery d where i.itemid=25905 and i.itemid=d.itemid;
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Is it ok by design?

This case should be considered from several points of view.

I've not checked this case namely but, for instance if hundred items (SNMP OID) have been not discovered anymore (missing in SNMP OID tree), why we need to pool it ?
Maybe I'm wrong in this example, but would be nice to definitely know that such behavior is ok.