Best I can tell they were counting four rivet in place members and one bolt in transmission cross member ???? There is a call out on the bottom of the frame chart that says: “Structural cross members: those are attached to resist torsional frame stresses” Guessing that means items like bed cross members are not in the 5 count.
Mine is missing the transmission cross member. Reposting my picture of the frame showing 4 members.
No bumpy roads.........but adding the cross member with trans mount can be added for $100. Considering adding the trans mount as a small winter project. I see several new cross members have notes in the description they work with the CPP disk brake upgrade.