Not suggesting closure of the airport to passenger flights would automatically follow. Some countries close everything, some don't. I just wanted to waive a warning flag at anyone planning to return to Hong Kong in the near future or planning to leave.
Even without formally ordering airport closure, an SAH I suspect would lead to reduced demand for flights and some operating hassles with crew, and that alone might lead to reduced flights.
I do think there's a real risk that that sort of talk by the professor will lead to hoarding and shortages in the shops in the next few days. Maybe not very wise in that respect.