I believe Zuckerberg's answer to that question was that such an ad would be banned. It's an explicit exception in the policy that permits lying in political ads, an exception that bans lies in service of voter suppression.
To the broader question, about whether all lies in political ads should be banned, the free speech argument against is that while it's easy to invent easy and obvious cases of lying, enforcing that policy in reality is very difficult and puts Facebook in the position of censoring speech that one side may consider a truth and the other may consider a lie.
He did not provide a bright line answer and hemmed and hawed quite a bit. He tried to reframe as “harm” but of course provided no clear definition there. So there’s “some” undefined policy that might maybe apply. He and the PR team really flubbed the obvious questions showing I think how uncomfortable and unclear they are internally about their policy and where to draw the line.
To the broader question, about whether all lies in political ads should be banned, the free speech argument against is that while it's easy to invent easy and obvious cases of lying, enforcing that policy in reality is very difficult and puts Facebook in the position of censoring speech that one side may consider a truth and the other may consider a lie.