Ok, first of all, the speed was probably faster than 20 mph. If somebody is telling you a story about racing, they will always add 20-30 mph, if they lose control of their car, they will always subtract 20-30 mph so it looks less like their fault.

Also, sounds like the person just sucks at driving, probably panicked and locked up. I've seen the exact situation at autocross, guy in a Miata started headin for a curb, locked up, and slid into it. If he would have let off the brakes the tires probably would have grabbed and he could have pulled out of it.

Anyways, IMO, driver completely at fault, and it was prolly a 30-40 mph crash, in which case the rim handled it fine.