Hello Skipperoo.

As per the Australian Tagging guidelines, thje local name should be used in these dual naming situations.

https://wiki.openstreetmap.org/wiki/Australian_Tagging_Guidelines/Roads#Dual_Road_Naming

Further, your contention that "all street signs show the Princes Highway name" is incorrect. There are many street signs which use the Lonsdale Street name. I have reverted your changes.
            ---
            
            Published using OSMCha: https://osmcha.org/changesets/135556690
            