I agree. This should not be surprising. The ability to link a file to a directory is different from the set of permissions necessary to change the data in the file.

Here's a practical example: I can create ~/public with permissions 777 (fully permissible) and allow my friends to read and write freely in it.

They can create files with permissions 600 (only they can read/write)

I can't open up these files and read the contents, but I can remove the entire thing from my home directory.