Passwords are not in Keychain, so how am I logging in?

I normally log into Twitter from my iOS device. I was trying to login from my Mac, and somehow, instead of logging in, I created a new account! (Annoying, I know!)

I'm trying to cancel the mistakenly-created Twitter account. So I go to twitter.com in safari on my Mac, and I am still logged into the new, mistakenly-created account.

In order to delete the account, it requires my password. So I look in passwords in Safari and I see only one account--a very old Twitter account that I deleted years ago!

So there should be three passwords in keychain – the oldest, the newer one and the mistakenly-created one.

What I don't understand is, how am I able to log into Twitter on the Mac and how am I able to log into the other Twitter account on my iPad when those logins are apparently not in keychain?? (Yes, all devices are connected to the same Apple account. No, I am not currently using a third-party password manager.)

(In the below screenshot, the password that is being filled in is apparently my old, deactivated account.)