This was discovered by Jim East:
https://slrpnk.net/post/27305276/18006810
I must say it fails the principle of least astonishment. If a user blocks Lemmy.World but subscribes to !linux@lemmy.world, for example, they obviously want to exceptionally see content in the subscribed community but nothing else from that node. But what happens is the instance block overrides the specific community subscription. So the general rule is prioritised above the specific rule.
And worse, when visiting the subscribed community it just shows no posts without reminding the user that they have a relevant block in place.

That doesn’t answer the question. To say “most obvious” just rephrases your position. We have a system that disregards user input because it thinks it knows better what the user wants. That can only be an “obvious” behavior if in fact you expect the system to be incompetently designed.
Calm down. Advertisement is a metaphor. If you don’t grasp it, just forget it. A capability is advertised to the user by giving them an option. Then failing to execute on the user’s instruction amounts to deception.
I admit that deception is typically a deliberate act. I did not mean to imply that. It’s safe to call it an accidental deception.
PEBCAK