ssh-agent should support '-c' and '-t' options of ssh-add

"OpenSSH for Windows" version
1.0.0.0

OperatingSystem
Windows 10 Pro

I've set ssh-agent service startup type to Automatic. I've also set a passphrase protected key at %USERPROFILE%\.ssh\id_rsa. The passphrase in question is not the same as my user password.
After rebooting my PC, if i type ssh-add -l I can see that my key has been loaded by default (without any prompt for my passphrase). I've also noticed that I can connect to ssh -T git@github.com without problems.

My question is: How is the ssh-agent startup service able to add id_rsa without asking for my passphrase? Is it storing my passphrase somewhere? If so, where?

I'm familiar with services such as PAM, as well as software such as GNOME Keyring, KWallet, etc. Just want to understand exactly what is the Win32 implementation doing and possible customize OpenSSH's security policy to ask for my passphrase at least once after login.

Start with the Win32 ssh-agent service and the ssh-add entry points mentioned in the issue, comparing the requested -c and -t options with the existing -l behavior. Review the discussion to reconcile option support with the passphrase and startup-policy questions; done should include a clearly defined behavior and corresponding validation.