I feel like that's true for early/mid-90s games where the PC version targeted DOS (+ the varied universe of PC video/sound hardware), and the Mac version could just target the much more uniform Mac platform.

But SimCity 3000 is from 1999, and the PC version was a normal Win9x game. I own (still have the CD) the SimCity 3000 Mac port, and it is not very good. Maxis didn't port it themselves, it was done by Software MacKiev. System requirements were quite high for the time, it was sluggish, often unstable, and the file open/save dialogs reused the Windows-style dialogs which was very awkward.

The soundtrack is great though.