Grant, as I understand it, it has to do with anything that contains a flammable liquid isn't supposed to be in a situation where if it's bumped or begins to leak on it's own, could cause a fire hazard.
They especially want gas lines and such protected, and I guess a sight glass (tube) on the side of a fuel tank is a little risky in their opinion.
Just another source where fuel can leak out.
They're death on bilge pumps for the same reason in powerboats, and should be.
The last time they inspected me, they asked about a fire extinguisher. I had one and showed it to them, but then I went on to say that because my craft was less than 30' in length, and my engine wasn't in a 'hold', it really wasn't required. I told them I have one because I wanted one.
They both laughed and then started asking me questions about the prop and the usual "how fast is that thing?"
Nice young men.
olf