It's still a concern. Attackers but knowing details can make attacks much harder especially if they attack things where they don't have any direct feedback it

It's still a concern. Attackers but knowing details can make attacks much harder especially if they attack things where they don't have any direct feedback it also increases the lightly hood of attacks been identified as such by monitoring before they succeed. Sure you MUST NEVER rely on obscurity for security and any form of obscurity for security which increases complexity is increasing the potential error/bug surface and as such a bad idea. But not freely giving out how exactly your bank works internally is still a very sane/usefull idea. (It's not the same as e.g. not giving out how a tool a lot of external people use directly works, it's about internal only workings which you don't give out.)