Wow, what a terrible example.

Their "physics English" version doesn't mention North and South; it just introduces the word "pole" without defining it. The average word length is considerably longer.

The actual verb in their sentence is rather far in. Overall, it's a more complex sentence. The "Plain English" version is targeted at an easier reading level -- presumably, targeted to its audience.

It's also weird that they're complaining about "physicists" at the beginning, and then comparing it to a "plain English" sentence. That's not a physicist writing; or if it is, it's a physicist acting as a teacher, not as a physicist. That has nothing to do with the way physicists communicate with each other.

TFA says that their version is "impenetrable", and gives the only actual good advice in the article: write to your target audience.