I don't think it is the case or now that the serpahim are following the given order shakka should have been able to order him stop then.
The override rule makes it so fellas of the same authority level can't override orders from each other
It is why Stussy wasn't able to stop them earlier and they needed a Vegapunk to do so
However if the Seraphim were successful with their order and destroyed the lab they would've been in a state for Stussy to give a follow up order
It is why Shaka can't give an order to make the Seraphim stop attacking the Straw Hats and such as someone on the same or higher authority level as him gave the order to attack. People think it is Edison since he's the last one to give an order to stop fighting but I'm trying to say if they completed that order then they're in a state for any VP level authority to give them another.
Which is where Devon comes in as she has the power to mimic people with her devil fruit, so she mimics one of the Vegapunks, probably the one that just got attacked, and gives a VP level authority order to attack the straw hats making it so now only the gorosei can stop it (or devon but she has no reason to).