Don't worry about them, you're correct. It's actually called an "accelerated stall", and every flight student learns about it. The term refers to a stall caused by an abrupt pitch change that causes the wing to exceed its critical angle of attack, even though the aircraft is flying well above stall speed. An aircraft can stall at any speed if the critical angle of attack is exceeded.
Anyone with any knowledge of aerodynamics should know this. It's very basic. That said, I don't know if this is what happened in this case as I have not viewed the video yet.
OK, now I've watched the video. Zot is absolutely correct. He was definitely stalled when he hit the ground, though it is difficult to tell for sure if that was what caused the accident or if he stalled it right at the end as he instinctively tried to avoid the oncoming ground. It was very clear, though, that as he approached the ground the aircraft was nearly level yet his velocity vector was obviously downward. That would mean that at least toward the end, if not earlier, the relative wind was coming from below and striking the lower surface of the wing at a sharp angle. That will definitely cause a stall.
I also noticed his left wing dipped right before impact which could have been due to the aircraft beginning a spin (which can only happen if the wing is stalled first). It's not entirely clear, though. The pilot also may have applied sudden left stick as he saw obstacles approaching.