I should have formulated differently, but English is not my native language, so.....
It is very evident that the stacking swivel were deliberately taken of by the GIs. According to many US combat infantrymen from WWII, I spoke to over the years, there were several reasons, some said that it was mainly because the stacking swivel could snatch up stuff, like low hanging wires or twigs and branches while going through a hedgerow or a stand of young trees. Others stated that they were afraid that the swivel wold rattle during a stealthy advance or a patrol. Anyhow, I guess that in the field the stacking swivel was as useful as teats on a hog.