I didn't watch the video, but that's retarded. I've always had a massive chest built primarily by bench pressing. And your hardly squeezing the muscle when you do flies, seeing as by that point in the movement you aren't even moving the weight against the force of gravity.
Current PRs at 242, raw w/ wraps- 525, 355, 605, 1485
Roboro tui, perimo vester adversarius
(Build yourself, destroy your enemy)