My Canon AE-1 Program, Elan II, Olympus XA and a number of others all had separate exposure compensation controls. Sometimes it was just a button or lever to adjust for backlighting. Then there are other simple cameras that didn't have EC per-say but had a setting for fill flash. You're probably right for older film cameras when EC first started to appear. When manufactures started to incorporate more electronic and fewer mechanical controls, EC became separate. That was before digital though.