three-eight-hotel wrote

"appropriate category & class ratings §91.109(b)" indicates to me
that Joe cannot legally be "the eyes" for Bob, because Joe does not
have a complex endorsement...

Correct?


Nope! "Category and Class" are from FAA Inspectors and Examiners,
"Endorsements" are from Flight Instructors.

Joe is legal as a "Safety Pilot", but not as the Pilot in Command.

Bob Moore