I still don't get the bit where you say 2 high is standard. It's not. Though US port infrastructure is special, it's very outdated/inefficient compared to pretty much the rest of the world.
It's from the article last time this came around [1]
"For instance, Petersen says, local zoning rules prevented the owner of truck yards in Long Beach from storing containers more than two high"
[1] https://www.npr.org/2021/11/03/1051773672/a-look-at-whats-ca...