Controls "free and full" is obviously, very important! "correct" is also critical, though less worrisome if there is no reason to believe that the flight control system has been "maintained" since the last time YOU flew it. If you have reason to think that the controls have been "maintained": Free, Full. Correct, and correct travel range! This caught me out a long time ago in a Cessna 206 which have been maintained, and I was knowingly maintenance check flying. Sure enough, the elevator trim tab did in fact move freely, fully, in the correct direction, but, with the wrong travel limits, and in the C 206, this creates a terrifying flight! - I blame the poor pitch control system design of the C 206 for this - induced maintenance error, and (for that model 206) too little clarity about checking the work.
In the mean time, the SM1019 sadly, is one of the types which would easily takeoff with the controls locked. Pour the power to it, and it's going to come off the ground whether you fly it off, or let it fly itself off. In my opinion, control locks should be designed so that achieving anything like a normal takeoff would be aerodynamically impossible without moving some flight controls. That way, you'd know during the takeoff roll that you were having difficulty getting it off the ground, and perhaps abort the takeoff. If pitch controls were to lock in a large nose down position, the pilot might realize that takeoff was impossible without control input - other than the then likelihood of a nose over in a taildragger - but that's still safer than getting airborne with the controls locked!
The SM1019 is a truly "fun" airplane to fly, with magnificent takeoff performance - but it has some unusual characteristics too, particularly in pitch. It will just fly off on its own, into a steep climb as long as the pilot controls yaw. But, once airborne, and depending upon takeoff flap setting, and C of G, could require near full down pitch control input shortly after takeoff to maintain a safe climb attitude. So if you're airborne, and cannot promptly apply nose down control, what you see in the video is a likely outcome, unless you reduce power drastically immediately. I opine that when the experienced professional pilot initiated takeoff in this plane, he was out to "play" and get an exciting takeoff, rather than "working" as a pro pilot, so he relaxed, and did not check the control locks. He overlooked that this airplane, more so than most, will bite.