https://www.zabbix.com/documentation/2.0/manual/introduction/whatsnew201

As starting from 2.0.1 zabbix frontend (on any menu) performs zabbix server reachability checks every 10 seconds - currently logged user will be always kept as logged in (lastaccess in sessions table will be refreshed).

Note that 10 seconds (cannot be configured by user) is less than 90 seconds (allowed minimum).

So the user profile option "Auto-logout (min 90 seconds)" will be sort of ignored till the browser is running/tabs opened.
It will be taken taken into account only after user browsed/tabs will be closed and reopened after Auto-logout period.

It's true when global config option "Show warning if Zabbix server is down" is enabled, which is true by default after installation.

Documentation has to be corrected for all versions starting from 2.0:
https://www.zabbix.com/documentation/2.0/manual/web_interface/user_profile

I'd change:
With this checkbox marked you will be logged out automatically, after the set amount of seconds (minimum 90 seconds).
to:
With this checkbox marked you will be logged out automatically, after the set amount of seconds (minimum 90 seconds).
It will not work in case when "Show warning if Zabbix server is down" global configuration option is enabled and zabbix frontend (any menu) is kept opened or when for example pages on Monitoring menu perform background information refreshes.