Your equator would have been cooked, with a massive die-off. The animal and plant species, the fauna and flora, would have thereafter been from the temperate regions, growing into the equator. Obviously your tropical forests have been around for eons. They are well established.
Fossils show their progression.
They did not die out, nor did they spring forth within the last mere 12,000 years. The analysis is correct, and the physical evidence undeniable, but the conclusions are flawed. If the poles were to be in mid-Canada, for instance, for a period of time, and then shift back to where the poles are today, the ice cores would represent such a change. Your frozen mastodons, within the polar circle, have grass within their bellies, showing that they grazed meadows at one point in the recent past, within 10,000 years or so as human scientists have estimated. This falls nicely in line with this new evidence.