Hey, look, a guy wrote a book about a non-sensical theory!
You are willing to bash a experimental psychologist, cognitive scientist, and linguist because you don't like a certain phrase?
As someone from the northwest I think you're hearing something that isn't there. They're said exactly the same. Some people understand what the phrase means and some people don't. The latter group uses "could."
No it is there, and I already quoted a linguist that explains the difference.