That is not the way to test among several accounts. It is very unreliable and/or unpredictable because the login is cached for the entire browser, not individual tabs.
The proof is that, after fully logging out, close and reopen the browser. Visit https://groups.io/ and login with a member account. Then open another tab and visit https:/groups.io/ in that tab and you will see you are automatically logged in as the same member as the first tab because the session is maintained for the entire browser window. Further proof is that logging out with the second tab will log you out on the first tab.
In other words, the only way to create reliable isolation is to use two (or more) browsers (such as Chrome and FF) or simply login and logout with a single browser.