Most of what comprises a port is infrastructure for handling containers and bulk cargo. If cargo volumes are down, some fraction of that infrastructure is disused, or used below its capacity. That a ship was at berth is cold comfort to the longshoremen, truck drivers, etc. who expected to work that cargo, nevermind to the people that expected to, y’know, purchase and consume those goods.
Is 30% underutilized / partially disused tantamount to empty? Maybe not. But it’s in the ballpark in a way the snopes rating undersells.
And here's the port of Seattle: https://www.vesselfinder.com/?p=USSEA001 You'll note a distinct lack of yellow. If you zoom out a bit you can find some 'bulk carriers' but those aren't container ships.
So when the article quotes the Seattle port commissioner who says "we currently have no container ships at berth" that might be literally true right now at that specific port.
Other US ports seem to be doing better - Perhaps Seattle is badly located or expensive, and has taken a disproportionate fraction of the 30% drop in volumes? There are certainly larger ports on the same coast https://commons.wikimedia.org/wiki/File:Top_container_ports_...
One sets off for a morning drive on Thanksgiving. Upon entering the freeway, they find the normally traffic-congested road smooth and free-flowing. The journey takes a little more than half the time it usually would. They exclaim "Wow, the roads are empty this morning!"
I'm playing a bit of devils advocate, but it's not inconsistent to observe a typically congested resource X operating at a fraction of its capacity, and note the observation with "wow, X is _empty_".
That's why it's just "mostly" false, but 'empty' is a word with a specific meaning, and claim here was that the port is literally empty of ships. (or, in the case of the Twitter message they show, that there's only one single ship in the harbor)
Is 30% underutilized / partially disused tantamount to empty? Maybe not. But it’s in the ballpark in a way the snopes rating undersells.