Timecard shows approved even if only one manager approves it

Summary:

One employee who has 2 assignments, submits a timecard for both the assignments. As per the approval rule setup, the bell notification for timecard approval goes to both the managers. Only when both of them approve the timecard from the bell notification, then the status changes to "Approved" from "Submitted" in Timecard history.

However, in case one of the managers, navigate to My teams>Manage timecard and approves the timecard from this page. The timecard status changes to
"Approved" from "Submitted" instantly - without waiting for the approval from the 2nd manager. Shouldn't the status be still in submitted until both approves? If this is expected, any document that supports this functionality?