Form 1s for SBRs aren't taking 12 months. More like 1-2 months. Form 4s and form 1s for suppressors are at 9ish months.As much as I hate to be the one defending the ATF, I really don't see it happening that way. They won't be opening 4 million background checks on day one, they'll be processing however many they normally process at once, so the system will be under no more stress than is already is.
Since Form 1s already take 12+ months we know that the background check must only be open for a fraction of that time, otherwise everyone would fail, no one would get an SBR, and everyone would be subject to enforcement action since failing the background check means you can't have *any* firearms, let alone an NFA weapon.