Hi sWoopSF,
Sorry I'm no expert with all the info, on the recovery key.
Seems that the recovery key is more for security use with your Apple ID account, than with individual devices.
Eg: If you need to reset your password, you can use your recovery key to regain access to your Apple ID.
A recovery key may help improve Apple ID account security,
but if the recovery key is lost ... account recovery can not be used.
Apple support's articles (links below) contain more details
While it’s not required, using a recovery key improves the security of your account
by putting you in control of resetting your password.
How to generate a recovery key - Apple Support
Learn more about using account recovery instead of a recovery key.
How to use account recovery when you can’t reset your Apple ID password – Apple Support (AU)
And
A recovery key helps you reset your account password or regain access to your Apple ID
How to: Keep your Apple ID secure on iPhone – Apple Support (AU)
All the best :-)