That’s about what I expected. It doesn’t make sense for any parties involved to enforce the 7 day deadline, including users. This is a reasonable solution.
It's just slightly disappointing that the CAs and browsers have agreed to operate under a policy that requires the CAs to revoke mis-issued subordinate CAs within 7 days (CA/B Forum BR 4.9.1.2), but that's not actually feasible in practice - at least not at this scale. Certificate issuance would need to be automated enough that it would be feasible to actually replace all certificates issued by the affected CAs within a 7-day period.
Let's Encrypt represents the state of the art in terms of certificate automation, but last time they had an (impending) mass-revocation event, it turned out that even the ACME protocol / client implementations didn't really have any concept of an automated "this certificate is about to be revoked, please re-issue" process. As a result of that event, certbot at least got support for triggering renewal after revocation: https://github.com/certbot/certbot/issues/1028#issuecomment-... -> https://github.com/certbot/certbot/pull/7829
I think it's not so much that it isn't feasible as that it doesn't serve any useful purpose at least to Mozilla.
The Firefox out-of-band revocation mechanism (OneCRL) certainly could revoke all these intermediates but Firefox isn't vulnerable to a problem here, so there's no obvious upside to doing that and it's disruptive.
