I read another take on this and what the ATF has a problem with Wyomings' definition of "expunged".
Apparently Wyoming does not physicaly destroy the records, and in fact they could be used to increase penalties should the person commit another offense in the future.
AFT is being pretty picky here imo, but then again I'm of the opinion they shouldn't even exist along with junk unconstituional gun laws like the Lautenberg Act.
Seems as though the ATF is correct on this one and that the intention of the Congress is that there be no record of these convictions kept. If the State can dreg it up again it is not expunged by definition.