does seem to entrench the principle that the Federal Security Service of the Russian Federation (FSB) can demand decryption
It also entrenches the principle that the Russian legal system isn't competent. Here's where this takes a turn for the silly:
The governments in most western nations like to talk a good game on crypto, they like to engage in hacking via security services. They like to sabre rattle about backdoors. A case like this wouldn't pass the laugh test in a western court room.
Why? Because western courts acknowledge the difference between choosing not to do something and not being able to do something. It's simply not possible (they could maybe ask Snowden for advice, given how much he trusts it) for telegram to decrypt user messages. Not without being backdoored anyway. It certainly isn't in the realms of possibility to do it retroactively, and that's why it wouldn't get through a court.
And that kids, is why Russia will always be regarded as a banana republic.