Funny discussion but some faulty logic going on.
I bet that guy practicing judo falls did not do so in order to be able to slip and fall on a hiking trail later on. It was an unrelated consequence of a skill learned for an unrelated activity. Training to fall on grass or concrete intentionally so you can later fall on your bike better at speed is something I can honestly say I have never heard of anyone doing.
Unrelated but related loosely is the idea of falling while climbing.
When I sport climbed I fell sometimes. It was expected and even encouraged in a sense because you could not really push the limits without doing so. Sometimes a specific sequence would entail falling many times until one figured it out. But, it was also relatively safe because we were usually top roped or on good pro(tection). While doing so one learned how to "fall". My risk aversion was fairly low in that case.
OTOH, when alpine climbing falls were strongly discouraged, even though we all knew how to fall, due to relatively unprotected leads and remote locations - but still somewhat expected and prepared for. I would say the risk aversion was moderate. Mostly we imagined we would know what to do if it happened.
When solo alpine climbing, falling simply was not an option. The chance of a successful outcome was practically nil so, although I knew how to fall from sport climbing, the parameters were different and my risk aversion was high even while participating in a high risk activity.
Somewhat similar to biking. If I am riding around the block I might try standing on the Handlebars and seat or using no hands (to impress the kids). If mtbing on a known trail where I might be found I might try to get a little funky. But, if I am solo touring far from home on a desolate hwy and have my years holidays and all my equipment dependent on staying healthy, I tend to take fewer risks. The reward of impressing no one in particular does not equal the risk of something small potentially screwing something up really big.
My last fall off a bike was going up the Crowsnest Hwy towards Manning at a speed of maybe 2-5 kmh. I was talking to a friend behind me and my wheel slipped off the pavement into soft sand and pitched me before I knew what happened. Landed half on the hwy (fortunately no trucks going by atm).
Gave myself an ouchy!
It happened just past here:
And here's a stretch of the old Hope Princeton Hwy we saw on that ride that has been closed to traffic since the mid 1960's due to a rockslide that swept across the valley. Very slowly the forest is reclaiming the road:
