Master password on startup can be avoided

Hello, I have set up a master password on my Thunderbird client and it asks for it very time I open up Thunderbird, like it should. Unfortunately, I tried bypassing the password prompt and it is very easy : Thunderbird loads a window asking for the password, but by simply closing it, Thunderbird still boots up. Once it's open, you can see the accounts. It asks for the password again, but if you close it once more, you can access the inbox of an account. It asks for the password, you just close it and you can access the individual emails. It creates a huge security breach and defeats the whole purpose of having a password on my local client, being that even if somebody gets their hands on my computer and inside my session, they still can't access my email. Worse, it cannot work as a deterrent : if you open Thunderbird, see the password window and decide not to try to open Thunderbird, by closing the window, you will still access the inbox like shown above. I use Thunderbird 78.9.0, which, I believe, is the most recent version. Thank you for any help, Paul