If so, this autocomplete data is populated by Chrome from any other site with an 'email' form field - eg. logging into HN.
Had you taken the suggestion, it would still have asked for a password, which Chrome wouldn't have known unless you'd logged in previously, or on any other machine you sync with.
Look for "Allow Chrome sign-in. By turning this off, you can sign in to Google sites like Gmail without signing in to Chrome" in chrome://settings/syncSetup
So if you're working from home on the same WiFi, or if your phone with the Google account has been connected to the work WiFi, Google could be thinking "Ah, they're trying to login, let's offer them their account as auto-complete!".
It's at least one speculation, who knows if they've bothered with such a thing. An idea would be to totally remove Chrome from the work laptop, reinstall it, open Developer Tools, and monitor what data comes as you're trying to login.