Why would the use of "Friction" devices not meet the requirement for "Locks"?
Knowing too many Fixed Wing Rules and concepts have been applied to Rotorcraft by Authorities.....could the "Control Locks" thinking really be an evolution of "Gust Locks" that are mechanical devices that stop the movement of flight control surfaces rather than the flight controls themselves?
If you apply sufficient friction there is no moving of the controls without a lot of force being required.
I suppose one would have to differentiate between commonsense definitions and approved definitions codified within an Authority's Legal Definitions such as Part One of the US FAA FAR's.
The UK Contingent loving complex application of rules, regs, laws, etc with over lapping jurisdictions should be able to enlighten us on how they approach such matters.