Torque reaction from the engine moving binding the sliding shaft causing seal and case wear making changing gears harder?
The motor is on rubber mounts so it makes sense to have the rod change on rubber too.
If it was fixed and the motor flexes it could probably knock it out of gear or change gears for you.
What they said
Unfortunately, if we make all these things rigid, things will fracture due to the torsional effect that the body and drive train creates.
Best to just use these cotton reels and not worry too much about why, bit like engine mounts or radiator support rubbers, vibrations are an annoying part of Moking. Well that's my thoughts anyway.
HP