The mac mini they bought with their own money to run their own stuff? Company policy doesn't apply to their personal computing.

I'm sure company policy would technically prohibit them from accessing company resources from their personal computer; or if it does allow access to company resources from their personal computer then their corporate tech policy very likely does apply to their personal computing.

If the executive bought it for a personal mac mini for personal use only, with no interaction with company resources, then the person probably wouldn't have told the story.