Correct 10 W. In fact there is currently within IFATCA a long discussion on ( or I should say against ) the use of "maintain"in R/T.
In ICAO R/T maintain is used in the phraseology to pass on essential traffic information.
While in the FAA (US) phraseology it is used to clear aircraft to change altitude.
there have been numerous incidents with US pilots in Europe and NAT already,similar to the ones you mention that it proned the debate. ICAO was advised of the potential danger , we are awaiting the answer. Their are never very quick though...