Yes, they are removed completely. When you factory reset the AirPods, they are automatically removed from your Apple ID and from Find My across all devices. The factory reset process specifically triggers an unlinking from the associated Apple account, which is why the option no longer appears in Find My on your Mac, iPhone, or iCloud.com.
This is the correct and expected behavior. The new owner can now set up the AirPods 4 with their own Apple ID without any issues. They will not see any connection to your account, and you will not see them in your Find My.
If you want to double-check, you can log in to iCloud.com, go to Find My, and confirm the AirPods are no longer listed under your devices. Since you already factory reset them and removed them from Bluetooth, you should find no trace of them left on your account.