I would not disagree with you there, customers have a tend to stretch the truth some what....But brings me back to commissioning & testing, You are testing a piece of life saving equipment as near as it would operate in a fire condition...You are not testing if a push button works.
I can understand your point on commissioning but in a domestic situation I doubt if you would find many householders prepared to pay to have their detectors properly tested and there operation checked periodically it is difficult enough at times to get them to replace the batteries because of the cost