I bought a super glide mostly for clearance when backing in tight spots. This is to avoid hitting the cab of truck and front crown of trailer. Since you have a short bed it would be advisable to consider the slider. I don't see how it would help going forward since the king pin stays front & center.
I would wait and have them check it with & without the slider because, 1- its a lot heavier to move around if you remove it and 2- it does not react quite as good and fast backing up.
I have a F450 utility body truck and had an awful time getting information on the right hitch from dealers and manufactures. Seems no one wants to commit to anything. I bought a slider and did not need it and could not return it.