on the Ls400 Mk 3 the wheels are actually directional, the slope of the holes can be seen quite clearly BUT as you say, the ignominy of that 5th wheel being at the wrong slope if ever used, and in 50% of cases, is more than many could bear
( I only know this from an earlier comment years ago when i was corrected on here and after careful looking did agree ...... but so what ! )
Malc