I can see Tom's point, on the 90 degree backing. At that angle, you are no longer backing, only pushing, and twisting. You can not back a bumper pull trailer at that angle either.
I've pulled FWs with 4 different trucks, 2 8', and 2 6.75' beds. I have never had a slider. One of my earlier FWs would come close to hitting, and would require a slight pull forward, before backing again.
I don't know if I could back my current FW into a 90 degree angle without hitting the cab, but I would not twist it like that, even if I could.
Jimnlin is correct, that rigs do vary, and some will require a slider, or even a sidewinder style hitch. One size does not fit all.
Center of my pin, over the axle center is about 41"s from the back of my cab. My hitch has 4"s of fore & aft adj. I have good clearance with current rig.
Under extreme conditions, I think extra caution, getting out more to look, etc, is the key, no matter what you are backing.
Jerry