The article does point to a problem caused by bad practices and props to that. Still, every logger framework out there writes exceptions using ToString, which contains both the message and the stack trace. In the specific case of aggregate exceptions, it will also include all inner exceptions, so the problem in this article happens only because the author is logging only the message and not doing a ToString, solving the problem by just awaiting the task in the first step.

Still, good article explaining there exists an aggregate exception and its purpose.