I'm happy to see the HIG (Human Interface Guidelines) referenced in the post.

I was unaware Apple still maintained such a document? There was a time when TOG's HIG [1] was the Bible for the Mac interface. UI nerds at Apple (and likely elsewhere) would enjoy debating/interpreting them for some project or another. (I don't recall anyone being burned at the stake but there were definitely discussions that could reach a heretical pitch.)

The HIG preached a kind of nuance and balance—when it allowed for somewhat less "staid" UI elements it would advise moderation.

This came about in an era when the graphical user interface was a fairly new thing to the public and inconsistency (Do What Thou Wilt) would only have destabilized the gentle adoption Apple was treading.

It was a marketable advantage for Apple as well. Consistency on the DOS side, as far as I know, came about only as companies tried to adopt familiar patterns from popular apps of the day. (Related: I talked to an engineer at Adobe about the hideous UI (my opinion) of Adobe Acrobat on the Mac and was told they wanted it to look like it belonged alongside the suite of Microsoft Office apps. le sigh.)

From 1992, see Page 72 for menu widgets: [1] https://vintageapple.org/inside_r/pdf/Human_Interface_Guidel...