Offmeshlinks and navigation layers

This seems like a bug to me but I guess I better ask first -

I have some static obstacles with offmeshlinks so that characters can get over them. I would, however, want only some of the characters to be able to get past them.

So I set it up so that the obstacles are in a custom Obstacles navigation layer and some characters don't have this layer in their walkable layer mask. The problem is - they still use the obstacles offmeshlinks even though I would expect them to ignore this route...

Is this a bug or am I missing something?

A.