Raycor Clear Bowl - Double Standard?

When I purchased my 40 year old I/O houseboat, it had leaky fuel tanks. In order to get on the water right away, I left the empty leaking tanks in the bilge and installed a temporary tank in the engine room. The new temporary tank was made of plastic, and certified by the Coast Guard. The surveyor who looked over my boat for insurance purposes also blessed the plastic tank.

I finally got around to removing the leaking tanks and installing a new custom made aluminum tank which was just about the same capacity as the two leakers put together. Thinking that I'd like to keep an eye on fuel quality while breaking in the new tank, I ordered a clear bowl Racor Gasoline Spin On Fuel Filter/Water Separator - so I could see if any welding stuff was coming out of the tank.

The instructions say you have to use a metal bowl with an inboard motor. Does this make a lot of sense?

Forty gallon plastic fuel tank is perfectly OK, but a 1/2 pint plastic bowl on the fuel filter is a NO-NO!