The problem is that you haven't identified PayPal's concern. It's not sussing out whether a conference is real or fake. All of the money is at risk even in a real conference, run by a trustworthy person. You want their evangelists to reach out to conference organizers. If they were intimately involved in every single developer conference worldwide, it still would not eliminate PayPal's risk. It wouldn't solve the problem.
The risk is that one single person holds a huge pile of funds for services that are supposed to be rendered in the future. That single person can skip out of town at any time. They could get hit by a bus. Their venue could burn down in a fire. Whatever the cause, there is a non-zero risk that the funds aren't used as intended or the event doesn't happen, and PayPal will be on the hook for hundreds or thousands of disputes and chargebacks from the purchasers.
This is why payment services for events like EventBrite don't work like PayPal. EB gets paid the money, and the event organizer has no access to it until after the event, when there's no chance of EB being on the hook for disputes for an event that didn't happen.
PayPal isn't in the insurance business. When it does allow a pre-sale, per the terms already linked in this discussion, they typically require a reserve. That means money can come into your account but you can't withdraw it. That's not malicious, that's the same thing EventBrite does. You only get the money after you've rendered the service it was paid for; it's protection for the attendees and PayPal. To expect anything different is to expect PayPal to act as a free insurer of events.