The problems is that this is a ruling on the technical deficiency of the rule - the ATF is essentially assuming more power than the controlling statute has ceded to it - rather than a ruling on the constitutional merits of the ATF’s rule.
IOW, when Biden breaks the filibuster to ban most semi-automatics (which is coming WAY sooner rather than later), the bump stocks will be expressly prohibited by statutory law and not dependent on ATF discretion, essentially mooting this case. It will never be heard by the Supreme Court.