Hi @Rising Flight,
Welcome to the Microsoft forum for technical support.
By default, an Inbox rule named Junk E-mail Rule is enabled in every mailbox, so what you have observed is actually the expected behavior. Because it's a hidden inbox rule, so it's not visible to end users from either OWA or Outlook client, and the "-includehidden" paramter is required in order for this rule to show up in the result of the Get-InboxRule cmdlet.
According to your description, I suggest you can use the command in the following format to delete the rule:
Remove-InboxRule -Mailbox smb@contoso.com -Identity "Name of the rule"
Please replace "Name of the rule" with the actual name of the rule you want to delete.
Refer to:Remove-InboxRule (ExchangePowerShell) | Microsoft Learn
Please feel free to contact me if you have any queries.
Best,
Jake Zhang