That's only because the antivirus/firewall products have access to your machine and install a root certificate on them, or more likely, are just using a browser

That's only because the antivirus/firewall products have access to your machine and install a root certificate on them, or more likely, are just using a browser extension to rewrite the dom on the fly. More succinctly, the phrase "man in the middle" kinda loses meaning when the man in question is your own computer.