One can do a lowside, that is losing traction (not even locking, but just overspeeding and then braking, even engine-braking) in a turn. But this point is basically the first that must be taught: how to enter and exit turns properly.
I think ADAC is just being lazy / or too much ass-covering. But I don't know. I'm self-taught and not in Germany.
The whole point of learning to ride is to train yourself to always be prepared and situationally aware, to maintain total awareness of what you are doing, what is going on ahead and behind you, and keeping being able to correctly react as fast as possible whatever happens. Thus fingers on the brake.
They are seriously out there to kill you. Be it distracted car drivers, sloppy road maintenance, stray dogs, bad weather, random idiots.. any of this will kill you if you relax.
An occassional lowside or two in one's first two seasons most likely won't. Given even a mediocre protection set, one will get away with a bit of shock and maybe needing a new pair of pants. And a whole lot of training of the kind no school can give. Like when to pull the front brake and when to just open throttle and hope for the best.
Besides there is a saying - if you do not crash once a season, you do not ride, period.
Which is a grim reminder of that if one does not push oneself, one is losing skill.
I ride for about 30 years already and this is true. Motorcycles are not safe and cannot be safe, safety isn't in the concept, and this is what we love about them.