It isn't that unbelievable. This came in direct response to the Black Panthers armed protest in Sacramento in 1967. The law came in 1968. You have to remember that power then, and still now in a lot of ways, was racist.
The 4473 still hasn't changed, so it still appears to be a felony to buy a gun from an FFL if you use recreational marijuana, since it would require lying on the form to get it approved.
The Supreme Court doesn’t have the power or the need to rewrite the form. Either the Executive rewrites the form to comply with this ruling, Congress passes a law ordering the Executive to rewrite the form, or someone answers the form truthfully, gets denied, and then sues the ATF. Depending on how the case is filed and relevant case law, the court can order the ATF to issue a permit to the plaintiff, or order the ATF to stop denying permits to anyone who is in a similar situation to the plaintiff. (The recent rulings about nationwide injunctions are directly relevant to this discussion.)
I know for a fact in Virginia you were explicitly told when getting your medical cannabis certificate from a doctor that you would then be ineligible for a concealed carry license.