Look at the line drawing I posted, there is no slip joint for the torque arm.
You want both the pivot and the U joint to be as close to in line as possible. The point of the torque arm is to control axle wrap.
If there is a bit of movement the slip yoke in the driveshaft handles it.
Lot to unpack here.
I guess the first clarification is a "slip" joint in this context means a joint/connection with enough play to handle some of the kinematics involved here, as there is no need for constraint of the torque in more then one axis.
I am not sure that in every case both the u joint and torgue arm chassis connection need to be oriented close, as that location plays a part in deciding the desired instant center.
And everyone should remember "axle wrap" also includes braking forces.
It is possible to use another separate above the axle arm for braking forces only, and then decouple the torque arm discussed here in this scenario, but this is getting above my pay grade.
