He must have had AMS prior to HACE and just kept quiet about it.
This is a common problem. The HACE victim either (1) does not recognize the AMS symptoms, (2) denies/ignores the AMS symptoms, or (3) there is rapid onset HACE without typical AMS symptoms. All these can happen at Whitney altitudes although 'by the book' HACE at moderate altitude is rare and is usually associated with longer exposure.
Here are the Lake Louise definitions about HACE Can be considered "end stage" or severe AMS. In the setting of a recent gain in altitude, either:
- the presence of a change in mental status and/or ataxia in a person with AMS
- or, the presence of both mental status changes and ataxia in a person without AMS
see
Lake Louise definitions
