A bit of stats and a bit of math are not that hard.

Really knowing your stuff in either one of those fields is hard, knowing them very well and knowing enough computer science to apply it all (properly) is more the work of a small team than a single individual.

People like that are rare. There is nothing stopping anybody from calling themselves 'data scientist'. Just like there is nothing stopping anybody from calling themselves software architect or system administrator.

In the end that's just people marketing themselves as good as they know how but that does not mean there isn't a sliding scale between warm body and excellence. I think that is the distinction the article tries to make.