Just for an example, I was using this with v1.4 of CHEX3.WAD, the same one that can be verified with the checksums here: https://doomwiki.org/wiki/CHEX3.WAD
This wad just so happens to be missing a P_END entry, so everything afterwards gets put into the patches group, this includes flats and map lumps that come after all of the patches in this wad.
Just for an example, I was using this with v1.4 of CHEX3.WAD, the same one that can be verified with the checksums here: https://doomwiki.org/wiki/CHEX3.WAD
This wad just so happens to be missing a P_END entry, so everything afterwards gets put into the patches group, this includes flats and map lumps that come after all of the patches in this wad.