That's not really the same thing as members of the public don't have access to such places!
Where they do, and the best parallel would be other transport such as aircaraft, ships and buses, you can understand why someone might be concerned about obvious dangers, such as a member of staff seemingly under the influence, messing about or behaving in an aggressive manner.
But there is no sense in passengers monitoring the performance of staff in the course of their duties, when they have had no training in, or real understanding of, those duties themselves.
You make some very valid, sensible and balanced points in this thread Greenback, thank you for that input!
I agree that passengers and members of the public, be they knowledgeable about the railways or not, have a right to expect the safety aspects of their journey to be handled to a high standard by somebody who is competent and conscientious about their work. Railway staff working in these areas must be aware of this and understand that they are in a highly visible role where there is every chance that some of their customers will take an interest in how they perform their duties. As an example, I was asked only a few days ago by a worried looking chap on board why the door open buttons were lit while the train was moving. It was a 158, and the buttons that he could see through the vestibule doors were in fact for the disabled toilet door! A silly question if you know your stuff, but an illustration of the sort of concerns that some travellers will have. At the same time though, it's worth remembering that the intricacies of railway operation are not intended to be public knowledge, for good reasons, and in many cases staff have every right to decline to offer details of what they might be doing and why, door operation being a good example. I've had people getting very curious about how the doors work, almost certainly with completely harmless intent, but they didn't get the answer from me.
There is never an excuse for slacking on the safety stuff and I can never understand those who do, particularly bearing in mind that the next passenger who notices something could very easily be a manger from within the railway, who really does know what they are talking about. However, in the situation mentioned I think it's a case of somebody with a little information worrying themselves unnecessarily over a technicality about which they probably don't have all the facts. There is a line where it becomes a case of 'mind your own business', and I would suggest that this one is probably quite close to it.