The execute bit on a directory

A mode is three triples: owner, group, everyone else. They are checked in that order and exclusively — if you are the owner, only the owner triple applies, and being in the group cannot give back a permission the owner triple denies.

chmod 077 file locks the owner out of their own file while everyone else reads it. That is not a bug; it is the rule.

On a directory the bits mean something different. Read is permission to list it; execute is permission to traverse it. They are independent.

A directory with --x can be walked through but not listed: you can read a file inside it if you know its name. One with r-- can be listed but nothing inside it can be reached.