Google AI says:

"Yes, flashing front bicycle lights are prohibited in Germany under the StVZO regulations. These regulations mandate that bicycle lights must have a steady, constant beam and not flash or blink. The reasoning is that flashing lights can be distracting to other road users."

So a rider with a flashing front light would be ticketed (at minimum) in Germany, which has a far longer history than the United States of bicycles being used by adults for daily transportation and thus has developed rational guidelines for sharing the roads.

And it's not only flashing lights that can be a problem. A poster here used to have as his signature line something like "I use ungodly bright lights because drivers are dim." Which, sorry to say, is just as self-centered and ultimately ignorant as drivers' "Bikes don't belong on the road" attitude.