Here is the proof.
RM 125 M and S
RM 125 A
RM 125 B
RM 125 C
As you can see in the photos the RM 125 B uses the same Torque Link as the RM 125 M, S and A models.
It does not use the 1978 RM 125 C Torque Link whick is a floating brake setup.
Looking at the photo of the optional aluminium swingarm it does not list a Torque Link to make the option viable. One could only assume that the standard RM 125 B Torque Link would bolt to the swingarm as per standard steel swingarm.
How anybody could think that this Suzuki aluminium swingarm is not period correct is beyond me.