Check the manual again. You have probably put the hubs on the wrong side. The hub labeled "R" (part E2) should sit on the
left side (on the arm labeled "L")
Why itīs labeled that way? Well, the TRF501X had the same parts and had the "R" hub on the "right" side.
So you donīt need the alu hubs to fix that.
The way you solved it is actually an option. Nothing wrong with that. Just a different setting "TRF501X style".
The alu hubs are Tamiya option part #53962. They offer more setting possibilities just like you say and are not left/right specific.