No, but you're only counting on one guy. A swarm style of defense, which most nfl teams use now, would have 5 guys around the ball by the time everyone knows it is out. You have to figure that it takes 3-4 seconds for everyone to realize the fumble has happened. A lot of time it just comes down to who notices the fumble first. If that person is near the ball, they try to scoop, and if they aren't near it they scream FUMBLE at which point guys just start knocking the crap out of any opponent near them because of the "if you can't get it make sure an opponent can't either" strategy.
As for that scenario you present, a lot of coaches will gladly take that risk because there is no downside. Either you get a game changing TD off defense or you have Michigan trapped inside their own 5. It's win-win and you go for the strip on the next play. Football is all about risk and percentages and when there are no negative scenarios you generally go for the gold.