My suspicion is that doing these restrictions for air and sea ports may be easier than for our land border. Also it seems like everything is on the table. Maybe more time is needed to ensure these exchange of goods and services aren't impacted by closing the land border.

As I was listening to the followup discussion by the ministers that was my charitable read - that closing the border would cause supply chain issues because truck drivers would be uncertain if they could cross the border or companies might not even attempt to send goods up... So I do agree that's a possibility, but it seems like if that was the emphasis it could have been expressed much more clearly.