This article makes it sound like mountain biking is riskier than hockey (in terms of spinal cord injuries), but without relative participation rates, one cannot draw that conclusion.
Spinal cord injuries absolutely happen, but I can think of plenty of sports that would have a higher incident e.g., surfing, skateboarding, motocross, horseback riding, gymnastics, cheer leading, etc..
It makes more sense for spinal injuries, but even that doesn't make mountain biking more dangerous than football (spinal injuries are relatively rare in football, but head trauma is common).
American football is played by a lot more kids than who mountain bike in just BC and isn't nearly as bad. (though some of the injuries from football to have lifelong effects that we are only now realizing)
Source: played hockey and biked in BC
58 mountain biking SCIs over 14 years (4.1 per year) in British Columbia 3 hockey SCIs over the same period (0.21 per year) in British Columbia
A casual hockey player finding themselves in a way too kinetic game of pickup can nope-out pretty quickly, or likely won't ever get into the situation.
A casual mountain biker can go on a casual mountain bike ride with his brother and find himself way over his head, then bouncing down the trail on his head, very quickly and without an obvious offramp. Ask me how I know... ;)
I broke the cardinal rule of new technical terrain: pre-ride, re-ride, freeride. You get off your bike and walk the feature to see how approachable and rollable it might be. Then you session it (ride just that one feature). Then you ride through it quickly as part of a longer trail.
I went 5 years without an injury. This one healed in 3 months. I believe I know what I did wrong and can fairly easily avoid making that same mistake again. Do I expect zero injuries in the future? No.
What I expect is years at a time of an activity that very much enriches my life, with occasional injuries. Hopefully more than 5 years at a time since I'm making changes to avoid repeating the same mistake.
And I wish people knew that downhill mountain biking is a lot like downhill skiing. You can take the greens down or you can yeet yourself off something that's tougher than a double black diamond. I've gone on many group mountain bike rides with people in their 70s. So like skiing it is something you can shoot for doing into your old age.