[oldE]

I suspect the biggest reason for the mystery of Antarctic vegetation is our shaky grasp of continental drift and the scale of time.
Think about how much you trim off your fingernails each week. The Atlantic Ocean widens by about the same amount. Consider how long your nails would grow in two hundred and fifty million years. That is approximately how long it has been since Pangea broke up, giving us the Atlantic. Was that the only continental drift event? No. Godwana predates Pangea.
Our sense of time is pretty limited.
Regarding written accounts. Oral histories of North American, natives on the west coast seem to have documented the last ice age with stories of sea level fall and rise. Can you imagine the craft of passing down family and tribal histories through that many generations?

Food for thought.
Best
Les