Migrating a user with the same SMTP-address as the CloudMailbox, which has been cleared bofore.

Question

Hey,

I have a hybrid environment with an on-prem exchange server and a synced M365 organization. I had the problem that one synced user had 2 different mailboxes. I followed the procedure from this article: https://helpdesk.realworld.net.au/hc/en-us/articles/16383110965145-Hybrid-Exchange-Removing-an-Exchange-Online-mailbox-when-both-an-on-prem-and-online-mailbox-exists-for-the-user

Now the second mailbox in the cloud is gone, and I am technically ready to migrate this user. I am afraid that a migration could inflict an error because the on-premise mailbox has the same SMTP address as the "deleted" one from the cloud. Is this command deleting the mailbox instantly, or is it still somewhere softdeleted in the exchange online?

Set-User <******@domain.com> -PermanentlyClearPreviousMailboxInfo