Reason

msDS-UserPasswordExpiryTimeComputed is a constructed attribute. It needs to be requested explicity.

Get-ADUser <username> -Properties msDS-UserPasswordExpiryTimeComputed, *

Explanation

Default properties are returned on all ADObject queries matching a specific type of ADObject (ADUser has its own set of default properties, ADGroup has it’s own set, etc.)

Extended properties are not returned by default but are implicitly enumerable static attributes on an ADObject.

Constructed attributes are not static properties but are calculated based on the values of other attributes belonging to an ADObject. I could not find any info on this, but I imagine that enumerating all Constructed attributes can be an expensive operation since the values are computed, and as such need to be explicitly requested via the -Properties parameter of the Get-ADObject cmdlets.

This all seems to be related to the systemFlags attribute on an ADObject, which is where the attribute types are set. From my testing, attributes with either the Constructed (4) or Non-Replicated (2) flag need to be explicitly specified to be returned from the RSAT cmdlets.

references:

powershell - Is msDS-UserPasswordExpiryTimeComputed a “hidden” member? - Super User