I’m not sure if you misunderstand how macOS accounts work or how FileVault works.

There are two ways to log into macOS: a local user account or an LDAP (e.g. OpenDirectory, Active Directory) account. Either of these types of accounts may be associated with an iCloud account. macOS doesn’t work like Windows where your Microsoft account is your login credential for the local machine.

FileVault key escrow is something you can enable when enabling FileVault, usually during initial machine setup. You must be logged into iCloud (which happens in a previous step of the Setup Assistant) and have iCloud Keychain enabled. The key that wraps the FileVault volume encryption key will be stored in your iCloud Keychain, which is end-to-end encrypted with a key that Apple does not have access to.

If you are locked out of your FileVault-encrypted laptop (e.g. your local user account has been deleted or its password has been changed, and therefore you cannot provide the key to decrypt the volume encryption key), you can instead provide your iCloud credentials, which will use the wrapping key stored in escrow to decrypt the volume encryption key. This will get you access to the drive so you can copy data off or restore your local account credentials.

> There are two ways to log into macOS: a local user account or an LDAP (e.g. OpenDirectory, Active Directory) account.

And just in case it wasn't clear enough, I'd add: a local user account is standard. The only way you'd end up with an LDAP account is if you're in an organization that deliberately set your computer up for networked login; it's not a typical configuration, nor is it a component used by iCloud.