Deleted Users

DaithiG 

The adaptive scope allows you to dynamically apply retention policy to a location based on certain attributes or properties of the mailbox(es) in that location, or sites for a SharePoint location. The attributes could be name, State or province, Postal code, Country or region, Email addresses, site name (for SharePoint location). However, the static scope apply to the entire mailbox(es) or SharePoint site(s) location.

So when a mailbox is deleted, the same lifecycle processes will apply to the mailbox, whether you use the static or the adaptive method, but you should manage the exclusion of the mailboxes from the policy by modifying its adaptive scope. To exclude a mailbox, first specify a custom attribute for the mailbox with a value, for instance, "Deleted mailbox", then include the custom attribute to the adaptive scope definition.

https://learn.microsoft.com/en-us/purview/purview-adaptive-scopes#advantages-of-using-adaptive-scopes

I hope this helps.