Thanks for reaching out about this, and great question. At the moment, I’m afraid we don’t support retrieving poll results in real time, though this is a great suggestion. For now, you webinar will have to have concluded, as you suspected: List Past Meeting’s Poll Results - Meetings - Zoom API - API Reference
Having said that, I think you raise a great use case, and I’d encourage you to share it in our #feature-requests channel, if you’re so inclined.