We saw one complete muppet having a picnic on the hard shoulder of the M20 once.
"Nowt as queer as folk down souf!

"
They even had a picnic rug laid out. Little table .... we could not work out if they'd broken down and NO they were not French heading to the port either. UK registered...
But in the case of the person changing wheel on central reserve... presumably he'd had a blow out and was unable to steer to the hard shoulder. He should have moved himself out of the way as soon as safely possible. and used the SOS phones for Trafpol to close off and activate the gantries and signals to close off L3 till that car was cleared.
Nowt as queer as folk.. it must have been M6 towards the South.. of course
But it does open up a sub-question.. what do you do if suddenly stranded in L3 and faced with prospect of crossing L2/L1 to reach the "safety" of the hard shoulder and have to abandon car .. which might also cause accident if stranded with hazards on in L3? Must be very very scary when that happens.