While this preference is mostly driven by capitalizing on the performance/price/size difference between desktops and laptops, it has lots of advantages when it comes to these situations.
My Dell XPS 13 only has 128GB of storage so none of the data exists solely on that device; it acts mostly as a dumb terminal that I use to SSH to my desktop. I suppose upon booting the machine they could request SSH key passwords and then search my desktop but this seems unlikely.
While most of the issues with these border searches are privacy/ideology based. These types of security theatre can easily be circumvented.
Of course, just using Linux may get you detained for a bit which makes it all moot. Maybe having a business card saying I'm a systems administrator (which is true) would make Linux an easy explanation.
If these searches increase and become normal, I think it's only a matter of time before Apple implements a cloud based 'data refuge' that would allow users to temporarily offload encrypted sensitive data to the cloud while crossing borders and traveling to countries with weak or no privacy laws.