> I'm pretty sure it should be "inheritable", because "inherited" on an attribute means the attribute is inherited, not the element's children will inherit the attribute.

That is one interpretation, but not the one I had reading it. I read it as "This target will be inherited by its children," rather than "This target is inherited from its parents," which, while a grammatical possibility, doesn't really make sense because you are specifying it right there with the equal sign.

Both "inherit" and "inheritable" have the same possible double readings. Something like "pass-to-children" or "pass-down" would remove the possible ambiguity, but I'm not sure like either better than "inherited".