What's funny is there was third-party software that would enable it on the Mac, Apple could have done it far earlier than MacOS X.

1993 PowerBook 145B (25 MHz 68030) https://www.youtube.com/watch?v=4cQo29SIIgU

1994 PowerBook 540c (33 MHz 68040) https://www.youtube.com/watch?v=peWIysrf7DY this one is a bit chunkier in the video recording than real life since enabling the external video visibly slows the graphics down