Did Factory Undercoat the Fuel Tanks?

I have three factory undercoated Mopars
All have a undercoating over the whole gas underside of the tank. Two ‘68 A-bodies and one ‘71 Ebody

all have original gas tanks.

This is because frame and trunk pan areas all around the gas tank are undercoated.

but I’ve seen other cars with less on the gas tanks.

Leaky transmission fluid can eat up the undercoating. And the leaks fly back into the tank