Pure Waffle Now - what has your onboard monitoring system got to do with following ATC procedure that is written in Black and White?
If you did get hauled over the coals because of said monitoring, surely if you demonstrated that you were flying in compliance with established ATC procedures they couldn't say much!
Many operators don't have on board monitoring !!! - Aircraft Type/Kind Of Operations is also irrelevant. Forget Heathrow/BA/on board monitoring/ The original question didn't mention any of these. Its a question of procedure .