If you look in the middle of your screenshot, you can see that you are telling Bitwarden to (manually) auto-fill the credentials for the current page. Thus, it shouldn’t be a surprise that Bitwarden is auto-filling the login form after you unlock. What you have disabled is (most likely) the option to automatically auto-fill as soon has the web page has been opened (“Auto-fill on page load”).
If you want to choose which set of credentials to use (e.g., if you have saved multiple login accounts for the same website), then you should unlock the vault first. When the vault is locked, all of the vault data are encrypted, so the Bitwarden shell extension (context menu) has no way of knowing what vault items you may have that match the current web page.
Unless you hate keyboard shortcuts, the easiest workflow is to forget about the context menu, and instead use the keyboard shortcut Ctrl+Shift+L. If your vault is locked, it will ask you to unlock. After the vault is unlocked, it will autofill the most recently used set of credentials. If those are not the ones that you want, just hit Ctrl+Shift+L again to cycle through the credentials available for that webpage.