Why are warrior arms designed like this?

Assembled my first box of warriors. Their left arms fit snugly in the socket. The right arms, on the otherhand, just hang out waiting for thr chest to hold them in place. They wiggle and if the chest isn't fully snug, they just fall out.

Why can't they both fit as pin in socket?

I ended up gluing that right arm on half of them. And may go back for the other half.