"Delete non-blocked session cookies" disregards the specified time interval (sometimes)

[ghost]

Tested with Kimai installed on a local host.

Settings in uMatrix (all Privacy check boxes on):
"Delete non-blocked session cookies 60 minutes after the last time they have been used"

STR:

1. Login to Kimai
2. Start an action (e.g. record activity)
3. Do something else in other programs for 10 minutes
4. Switch back to browser (chromium on Linux)
5. Refresh the page - Kimai asks for login

Sometimes it happens after 20, sometimes after 30 or 40 minutes (meanwhile session is active and works fine). Without uMatrix Kimai never logs me out like that.

At the same time: if I exit the browser completely and start it after say 2-3 hours - I am still logged in. Similarly even without exiting the browser: I am still logged in at sites which I closed more than 60 minutes ago.

IOW (speculation) it looks as if uMatrix deletes these cookies based on some fixed time and based on whether there is a tab with the particular site open rather than based on "last time they have been used".

It would be good to be able to have per location control (enable/disable) of non-blocked session cookie deletion just like we toggle the other things in the matrix.