I think a lot of these are very conservative estimates, like the oldest date there is hard evidence for. Like with the coastal travel to the Americas bit, there's a growing body of evidence that would put that at closer to 30 or 40 thousand years ago just because there are sites in the Americas that seem to be that old and "coastal boats" are the best theory since the land bridge was blocked by ice sheets, which would necessarily push back several earlier points in that chain too.