one wonders whether the regulations are remnants of practices that posed a safety issue in days gone by (over-wing refueling?).
I don't think you need to wonder, clearly it is.
Restrictions (eg fire truck present or the idiotic disembarcation described above are at best antiquated jobsworth and one suspects often job-justification and money mulcting schemes.
Usually a sign of a backward and stifling bureaucracy in my experience.