Did you watch the video?
The servers in the video don't look like real pros to begin with, the challenger gets multiple chances on his forehand side always from the deuce court, still misses every one except the seventh serve, which seems like a pity serve done for the video. Any decent player will mix up where you serve and make it hard for you to guess. I can guarantee that your challenger will have no chance if the serves were coming to his backhand, or body.
If you have some athleticism and a decent hand-eye coordination, you can even get a hit of a 100mph fast ball after some (a lot of) practice. But if you take one of the yarders here that is not a pro or college level player, they will have no chance of making contact with an 80mph pitch.
Go find those videos/links where the guy serving offers $100 (or $1000, I forget) for someone to return his serve, you can see no one succeeds.