Quote unlock based on User session timings

According to Oracle documentation, if a quote is locked and the user session times out, the quote should be automatically unlocked. However, there are some inconsistencies with the timing.

E.g - I created a quote (which is locked with me), and after 15 minutes of inactivity, my login session timed out. When I logged in again, the quote was not immediately unlocked; it took an additional 3 to 5 minutes to unlock automatically.

Has anyone experienced this?