It wouldn't be passively intercepted. It could trivially be actively intercepted. Gmail would not display a warning in this case, thus making the user think their password/reset URL was safe when it really wasn't. And trying to inform users about the difference between passive and active interception, and expecting them to make a risk evaluation based on it, is just not realistic for the vast majority of users.
That's not always true, and with more and more hosts supporting key pinning technologies like DANE, it'll be less true with time.
My mail server is set up to know that mail to Google domains (and others, like those hosted by Google or Microsoft) must be encrypted and the certificate must be correct. I occasionally look through my server logs to find more domains I can add to the list.
It wouldn't be passively intercepted. It could trivially be actively intercepted. Gmail would not display a warning in this case, thus making the user think their password/reset URL was safe when it really wasn't. And trying to inform users about the difference between passive and active interception, and expecting them to make a risk evaluation based on it, is just not realistic for the vast majority of users.