A trivia not touched on in the article - IBM 5 1/4" floppy drives had dual heads and could read the front and back side of a disk without flipping. For cost savings Apple ][ drives had only one head so you had to flip the disk occasionally. But to convert an IBM 5 1/4" floppy for dual sided used on an Apple, you had to cut a second write-protection notch, either with scissors, and xacto-knife, a hole punch, or with a dedicated "drive doubler" puncher.

https://atariprojects.org/2019/06/28/make-floppy-disks-doubl...