They weren’t part of the original set of Mac shortcuts, and couldn’t have been. The keyboard of the first Mac didn’t have cursor keys, nor did it have a control key (https://en.m.wikipedia.org/wiki/Apple_Keyboard#Macintosh_Key... ).

Cursor keys came with the numeric keypad; IIRC, control keys debuted with “Saratoga”, the extended keyboard in 1987 (https://en.m.wikipedia.org/wiki/Apple_Keyboard#Apple_Extende... )

I’ve read somewhere that they’ve been there since the NeXT days.

The Cocoa Text (Input) System maps shortcuts on Cocoa method selectors via a plist, so it makes sense that it originated at NeXT.

https://www.hcs.harvard.edu/~jrus/site/cocoa-text.html