80/90 LSD GL4 is not a problem for the clutch. The formulation is good for a limited speed differential and when you used this sort of oil you have no problem with the clutch.
API GL5 is not good because it whash too much

Today oil gear box is not a probleme with bronze you have always part in bronze like forks and bearing and the formulation is better than in the seventies year.

I thought that your hypoïd oil was GL5

Gl4 is 80/90 LSD. On my RM I have a good engine with a 5 gear box inside but my clutch is a 4 disques I need to put this sort of oil for not slipping that is better .on my RS I have a fives disques and need to be always repaired.I have change oil by LSD oil and now I have no problem