No disagreement that it is unlikely to have any effect other than a potential slight delay in all 3.
But, companies just do not do this type stuff on a whim. While us golfers don't piss off mother nature, drug companies don't piss off the FDA.
The only rational reason is to fire a preemptive first shot at the FDA to avoid an "MNTA only" approval (since otherwise any bias would work to their benefit).
So the important point is that Amphastar was sufficiently concerned about an MNTA only approval that they would take this step. And what caused them to act now (rather than earlier)?