Article 50 = EASA, so wording is copy from Part-FCL
Article 50A = Non-EASA so National rules
I think EASA cocked-up by stating something "act as pilot" and then
not defining it - therefore definition is open to interpretation.
"Licensed to operate an aircraft" is one definition, but here are
another two (from internet dictionaries):
One who operates or is licensed to operate an aircraft in flight
A person who operates the flying controls of an aircraft