Yes, it's correct.
If you only remove a user's license but don't delete the account, the content in the user's OneDrive will remain accessible to you even after 30 days.
Before you delete the account, you should give access of their OneDrive and Outlook to another user. After you delete an employee's account, the content in their OneDrive and Outlook is retained for 30 days. During that 30 days, however, you can restore the user's account, and gain access to their content. If you restore the user's account, the OneDrive and Outlook content will remain accessible to you even after 30 days.
For more information, see Overview: Remove a former employee and secure data
If your organization needs to retain mailbox content for former employees, you can turn the mailbox into an inactive mailbox by placing the mailbox on Litigation Hold or applying a Microsoft 365 retention policy to the mailbox in the Security & Compliance Center and then removing the corresponding Microsoft 365 account. The contents of an inactive mailbox are retained for the duration of the Litigation Hold placed on the mailbox or the retention period of the retention policy applied to it before the mailbox was deleted. You can still recover the corresponding user account for a 30-day period. However, after 30 days, the inactive mailbox is retained in Microsoft 365 until the hold or retention policy is removed.
For more information, see Overview of inactive mailboxes
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