I would say the contract situation with Moyes at United was vastly different to what Koeman has here.
Moyes would have crawled to OT on his hands and knees and signed the contract with his own blood, agreeing to just about owt they insisted on writing into it.
Koeman, on the other hand, was only persuaded to come here at the end of a protracted saga which ended up with all kinds of ridiculous money being chucked at him and at Saints to release him from his contract there.
Moshiri became obsessed with the notion of “four elite managers in the north west”.
Even when Ronald deigned to accept the job, he couldn't be arsed breaking off from his holiday to come and sign up in a fanfare of trumpets.
In those circumstances, I would be willing to bet Koeman as good as wrote his own contract and that he has a full pay out in the event of dismissal at the very heart of it.