Are devices supposed to automatically be removed from iCloud when all content and settings are erased? I've just upgraded to a new iPhone; my previous device was linked to my iCloud account, and had Find My enabled. When choosing to perform a reset (from Settings/General/Reset/Erase all Content and Settings), I had to enter my Apple ID password; the text on this screen stated that this was to disable Find My, which has been done. However, when checking the devices still associated from my account on my new iPhone (from Settings/My Name/iCloud), I noticed that I still had my just-erased device listed, as well as two Apple Watches (one that I'd erased several minutes before doing the same to my old iPhone, and an old Watch that I erased this time last year).

When erasing a device, are these devices then supposed to automatically be removed from the list of associated devices in iCloud or should this be done manually? When erasing my Watch, I clearly remember the notification stating that Find My would be disabled, as well as the Watch being removed from my account but this doesn't appear to be the case - for either my Watch or iPhone.
In a word, no.

Simply erasing a phone does not remove it from your list of devices in iCloud, nor does removing it from "Find My."

You have to go into iCloud and purposefully remove it from the list of "my devices" to indicate that you no longer own this device.

Just because you erase a device does not mean you no longer own it. Especially as erasing a device is often a valid troubleshooting step in finding problems with an iOS device.