That I think may be true, Greenland at its warmest was still not paradise but you could fish, grow wheat, farm and grow sheep. Then the ice took over.
The writer meant that Greenland was still a cold and desolate place and that the Vikings were being deceptive by naming it Greenland just to get more people to settle there.
I agree with you that Greenland truly was “Green”. At least around the edges :)
They also had a settlement around the same time at L’Anse aux Meadows in Newfoundland.