Unable to assign cash generating unit to asset with amortized adjustment.

In testing R12, I tried to assign 3 assets to a cash generating unit via ADI.  The "Post Adjustments Interface" program errored out for 2 of the 3 assets.  Log file indicates that the reason for this error is that 2 of the assets have amortized adjustment (which they do).  I just want to confirm that an impairment transaction cannot be performed on an asset with an amortized adjustment.  Is an impariment always an expensed adjustment so you cannot perform one on an asset with an amortized adjsutment?  Is this limitation mentioned in the manual?