> Now there are two partitions on the drive, Macintosh HD, as before, and Data, and it’s not clear if you need to wipe out just one or both.

Isn't this a feature of Catalina, not M1 Macs? At any rate, the author is acting purposely obtuse (not unusual for Thurrott). The process takes a few steps, sure, but it's not like you can't just google "prepare mac for resale" and it lands you here: https://support.apple.com/en-us/HT201065