But have you ever ridden a descent with no corners at all? I have. Here it is on the map. And here is a photo of the top with an elevation sign. It's a desert pass over the Altyn-Tagh. The word "pass" is being used loosely here. It's actually one way slope up onto the Tibetan Plateau. 8000ft elevation change top to bottom. Most of it is dead straight on alluvial fans. Part of it is through some rocky hills but the road is engineered for high speed traffic so the curves are large radius and don't require cornering. You can get a tuck on this descent, never touch your brakes, and bomb 50+ mph the entire way down. But you won't do that because you don't have a death wish right? What if you hit something on the road and blow a tire at that speed? You're dead.
I don't know about that pass since I haven't been there, but suspect I'd be tempted to let it roll all the way down if the surface was decent at all. I have done so on some a long descents with at least one of over 5000' of descending in the Sierras with only some minimal braking for the high speed well banked and wide switchbacks. It was a blast. I do have a long history of risk sports including but not limited to a variety of motorcycle and bicycle racing disciplines. I was never a very good bicycle racer, but did descend like a demon especially on a MTB or in a canoe or kayak. I have been accused of having a death wish pretty frequently by my buddies and compeditors. So suffice it to say, I tend to like to let the speed max out.
As far as certain death from a 50mph crash. That is nonsense. The biggest danger would be from going over the side of a dangerous drop off at any speed even a lower one, or blowing a turn and hitting a stationary object. From your description it sounds like the liklihood of that is low there.
By the way if you have panniers on the bike i'd question the 50+ miles per hour. It is pretty hard to get to that speed due to the aero drag IME even if you tuck.