In the Web UI (version 11.x of the firmware onwards), the way the SNE treats VLANs has changed from the behaviour in earlier releases.
Prior to version 11.x, for traffic that contained VLAN tagging it was necessary to use a VLAN Filter to tell other filters “downstream” of it in the map to increase the offset from the start of the packet by 4 bytes when performing their pattern-testing. If the VLAN Filter were omitted, other filters would not account for the additional 4 bytes that the VLAN tag introduced into the packet header and therefore wouldn't work.
From version 11.x (the Web UI firmware), all filters are able to detect the presence of VLAN tags in the packets passing through them and adjust their offset automatically to account for the extra 4 bytes in the header. So while VLAN Filters are still useful for filtering on specific VLAN IDs and priorities, they are not required to ensure correct operation of other filters.