Continental Drift not withstanding.
55 million years ago, North America was somewhat farther South than today. I believe these climatologists are trying to deliberately mislead people now.
The antarctic is about in the same place and, 10 million years prior to the time frame described in this article, there were dinosaurs and subtropical vegetation. It would also depend on what parts of the artic they looked at. Only some of it was more southernly, not all of it.