270 WSM or 300 WSM with factory muzzle brake

I own three Savage rifles with muzzle brakes:

A 270 WSM with an inside diameter at the end of the brake of about 0.415 in. With a 0.277 projectile, the bore is about .135 overbore.

A 300 RUM with an inside diameter at the end of the brake of about 0.335-0.340in. With a 0.308 projectile, the bore is about 0.030 overbore.

A 338 WM with an inside diameter at the end of the brake of about 0.375 in. With a 0.338 projectile, the bore is about 0.037 overbore.

Measurements were taken with digital calipers, however, I am an amateur so some small amount of error should be expected and those numbers should be taken as “ballpark” estimates.

My question is how and/or why does the brake on the 270 WSM have the larger diameter when it is pushing the smallest projectile? I’m certainly no gunsmith, but I’ve been trying to research online and what seems to be the consensus is that 0.020 overbore is optimum, 0.030 overbore is good (extra safe), and performance of the brake drops considerably after 0.040. The latter two rifles certainly fall within those guidelines, but the 270 WSM has almost 7 times the minumum overbore requirement!

Savage has one part number for the (inner) brake for the 300 WSM and 270 WSM and one part number for the (inner) brake for the rest of the 30 cals.

Anybody else have a 300 WSM or 270 WSM with such a large bore at the brake? I'm wondering if mine wasn't meant for a .375.