The approach can vary a little but it is polite, safer and easier for the crew if their very limited galley area is kept clear of passengers. On G-GATs there is very little scope for doing this and longhaul it can be an impossibility to keep the galley area clear. And some crews are just more relaxed about it.

The incident referred to relates to a 747 Upper Deck flight to Kenya. Bryan Ferry and family got caught up in it but the context was very different.

Some solvent based cleaners, if used in excess on baggage, can set off the sensors. Some people apparently clean their shoes with solvents!