This is, from what I know, somewhat accurate, at least the bit about lumpy food. But you don't need to be doing lumpy food at 6 months (you don't need to be doing food at all at 6 months!). I think you really just need to be doing lumps by a year or something.
A friend of a friend is a speech therapist, who has been seeing a fair number of two-year-olds or older who only eat purees and crisps. They never push food around their mouths with their tongues, so they have speech problems. I've also heard of this problem from my friendly neighbourhood bfc.
I've never heard the bit about not scraping up food off the face.
For what it's worth, my DS2 never really ate purees, as he didn't like them. Straight onto real food. Today he ate Thai food, and was very enthusiastic about crab claws, and fish cakes. He's 10 months, just.
You can use some purees and some lumpy stuff. Your baby might not yet be ready for lumps, try and see. You can use purees as pasta sauce on pasta - you can just give penne or fusilli and let your baby use that as finger food. It's pretty messy, though.