Don't look now, but he DID make a mistake in a preseason game... and don't look again, because they really didn't give Felix many snaps at all... but that couldn't POSSIBLY be by design, and attempt to keep what they have in the way of special packages for him under wraps...
You still miss the point, which is that maybe, just maybe, the Cowboys know what they're doing... maybe, just maybe, they have a carefully planned out approach to preseason, including holding training camp where the weather is cool, so as not to burn their players out... perhaps they believe as an organization that you want to do what you can to keep your key players healthy, ready for the regular season...
But NOOOOOO, you seem to want to assume that they're just a bunch of incompetent putzes who know less about the game than you do...
Excuse me while I laugh sarcastically at that...