Yep, that threw me a bit, too. I always double-space at the end of sentences since it's standard manuscript format. Any other method is wrong, damnit.
(Reviewing this message, my double-spaces were converted to single. Curses! Phooey! Indeed, phooey!)
Actually, I was taught it was wrong to double space on computers (not typewriters mind you) because the system automatically accounts for the extra space needed to emphasize a new sentence.