That is probably because DL only understands the meaning: Following. They completely forget the other meaniiing of the word: "Beachten", meaning something like "carefully looking at something" , loosly translated as studying, considering, actually a little bit more critically looking then only following. After having studied the rules following them is only one of the options. One could also criticise them, or trying to get around them.
I thought "they take notice of the rules" was O.K., but the owl thought otherwise
Probably because .. to take notice of ... is a too light interpretation of "beachten".
"Beachten" wich is related to "Achtung", which means something like: "to honour", "Respect", something you have for red lights in your car, or on traffic signs, or for your higher managers, maybe your parents. You don't just notice them, like they are irritating bugs. It is more that their wish is you command.
See also what google translate says: https://translate.google.com/#de/en/beachten so "to comply" would be the best translation.
And Germany is originally quite hierarchical, militairy. So "to notice" is not fitting in this culture.
Because it is like driving a car and observing the traffic rules. "Beachten" is more then just observing them. It is following them. Trying to drive on the right side of the road, things like that. If you look at the word "beachten". Technically it means something like "to acht". Which means something like "to honor". Like what the bible says you should do to your parents. The word "Achtung" is related, which means "attention." Attention in a way like attention they are shooting here. And there are mines. So attention dangerous situation. Beachten is like paying attention to the dangerous situation following rules to keep save. Not like in a movie-situation but like a participant.