I could be corrected on this one, but I'll give it a try.
The difference is permeability of the hose, and the concern is gasoline. A1 has a higher standard, and does not bleed gasoline at the rate that A2 does. A2 is the old standard, what we've been using.
You're dealing with diesel
. I don't think that some diesel sitting in your long (and I'm guessing not gravity clearing) hose is going to be a problem. It's not going to fill your engine
compartment with flammable fumes.