Given the hare problem is it probable that the 3" 20 was introduced there partly to provide a heavier load for that purpose?

I have seen hares cited as one reason for the tight chokes on Euro guns meant for Euro use, along with foxes and the several species of black grouse, which they take like we do turkeys. And I notice that most of the few 20s that are offered for European use are 3" chambered.