No, it works. I described above "how exactly" and "why so".
The question is what is considered "inactivity" - rhetorical.
Some clients have pages in a box that are updated once a second and the person just sits and looks at them without clicking anything. For example, the remote control of a security company. There, a person just sits and looks at the page, which is constantly updated, and when an "alarm" pops up, he takes a walkie-talkie and calls an outfit. And this company has a checkmark "deactivate in 10 minutes". If a person closes the tab in the browser, then yes, after 10 minutes he is not active. But while it is open - it is active.
If we remake this logic now, some of the clients will suffer, they will receive the same theme "I did not close the tab, but I was deauthorized - it does not work."
The only option is to rename the first checkbox to "Deauthorize if browser tabs are closed for more than N minutes", and add a new checkbox "Deauthorize if inactive for N minutes" already according to the logic you ask.
But, this is a refinement, and the party policy allows this only for paid users:
https://crm-onebox.com/ru/support/ofitsialnie-novosti-onebox/1487-besplatnie-dor...