Well. There's truth in it and there's not.
Holden took the Opel Rekord and said It's a bit **** but I reckon we can do something with it. Actually they took most of their cars from Europe or UK and made them into something far better.
they used stuff from both the rekord E and commodore C for the vb commodore in 78 but the actual name "commodore" was sold on opel vehicles a decade before it was ever used here starting with the opel commodore A in 67.
the first commodores were literally the same thing as the zb, imported but at least assembled here, played around with to suit the conditions and a holden badge slapped on it but they were still opels.
even branding like omega and senator were pulled from old opel models but we should expect that from a multinational company like gm because it is easier to use what you have rather then create and trademark new.
when the commodore was first introduced here it was considered "your wifes car" or not a real holden to the enthusiasts
the zb will always be that imported insignia and they should have just left the name as insignia but some genius thought commodore would work lol
at its core the v platform was an opel thing until 2007
en.wikipedia.org