Whomever started this "Louver not open enough" silliness should be "spanked" . I'm sure any flow calculation would show the centertubes flow capability multiple times that of he preceding media.
Guess you have missed seeing many of the photos posted in this forum showing examples of nearly closed louvers. No thanks on that, I'll always inspect louvers before buying a filter. Choked down louvers will increase delta-p and make bypass valve events more prevelant.