"I haven't got through Harker on Sharp yet. Why was he discussing the population or size of Sharp's villages? And why is it so important if these 'statistics' are inaccurate, apart from the inaccuracy generally casting doubt on the quality of Harker's work?"

I think you'll understand more when you've finished reading Harker, and also Bearman's critique (linked in my post). How significant the argument was is a matter of opinion.