Many people do this - take a look at any children's show where they read books out. Typically the spoken words don't match the page exactly, but do carry the gist of the story. I do the same thing when I read to my kids, my brain summarises a sentence very quickly, and I repeat it in my own words without thinking.

I think this is just part of spoken communication - our brains short-circuit more formal written patterns into 'normal' speech patterns.