Lower Control Arm at Torsion Bar Socket

Good evening all,

Cleaning up a couple sets of lower control arms. Realized that 3 out of the 4 arms have a collar at the torsion bar socket. 1 does not. Has anyone else ever come across this? Arm without the collar seems to be slightly looser.

First picture shows without the collar, one shows with the collar.

Apologies if terminology is off.

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