Looking into external documentation page, I found this L7 Filter (GPL) link to ClearFoundartion's page. My question about this topic is that this feature was already removed from Openwrt. At the best of my knowledge, there is no L7 Filter feature or package available for Openwrt so far. So It isn't it a miss information?
Yes, the l7 filter package has been long obsolete.
I have removed the section regarding L7 now.