The Offscreen terrain pre caching slider should have came with SU5 on PC.
My best guess it it was not quite ready and Asobo had to meet the XBox launch deadline come hell or high water.
My hope is now that we have the performance enhancements of SU5 and (other than the night lighting bug) fidelity of SU4 that future SU’s can focus on bug squashing and fully tested and vetted performance enhancements and new features. If there are any potential issues with SU6 that fix/feature should be dropped or the update pushed back.
I’m happy with WU6 and where the sim is at now vs SU5.