I’m personally not into Midnight Oil, but if the new versions are indeed
remixes of the old albums (if that'what you mean by “musically different”), then it's really strange if they remove the original versions from the streaming platforms.
Just to make sure we are comparing apples with apples...
Remix: Elements in the songs are added, removed, or panned differently.
Remaster: The tone is changed by EQ, and/or the dynamics are altered in some way but the mix is still the same.
So what exactly was changed in Midnight Oil’s songs?