AuthServer in Exchange Online

The result of Get-AuthServer is different between on-prem and EXO. The list of objects from EXO get-authserver includes some "IssuerIdentifiers" that include a "{tenantid}" pattern. Was this supposed to be expanded by a script, or by HCW? (HCW has never run to completion without exceptions.) There seems to be no documentation about this: no list of default entries, no documentation on the expected form, few mentions of the use of Set-AuthServer/New-AuthServer, and the options don't match the properties.