Sounds spot on to me. It is holden, so from the factory it has 'soft' valves. They help make the complete package with 'crap' piston rings, 'dodgy' transmissions and 'wannabe' magna styling.
Really though, any car that runs on unleaded from the factory would have hardened valve seats. Any older engine running unleaded should have them too, same goes for LPG. The lead in the old fuel would protect the seats, since it was removed every car has to run the hardened seats or the valves will eventually wear into the head.