CI 4.3.5 - Session Expiration Not Working

Okay, your issue is that the session cookie in the browser is not deleted.
You can check the expire datetime of the cookie in developer tool in your browser.
Check it.

For example:
ci_session:"phc6i4r70sbsq04vhpfp9tdkui866m3b"
Created:"Wed, 17 Jan 2024 09:54:32 GMT"
Domain:"localhost"
Expires / Max-Age:"Wed, 17 Jan 2024 11:54:32 GMT"

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