Logout does not log out of existing OpenAthens session

When you log into GS through OpenAthens, the click logout, you're logged out of GALILEO, but not OpenAthens. I tested with Agnes Scott College and the University System Office. I logged in, then logged, out. I was told I was logged out of OpenAthens, but still had an current session. I went back to GS and was able to authenticate as ASC or USO again without logging in again.

In both these cases I am logging in using the institution's IdP, not my,openathens.net. If I log in using my.openathens.net, I am logged out of OpenAthens properly.