YC has proven an accelerator works when teams move to be part of it. That doesn't prove that investing in companies that are based elsewhere and take part remotely doesn't work though, or that moving was a contributing factor to success, or that founders who are willing to move are demonstrating a greater level of dedication (just a different sort of dedication).

To know whether remote will work YC needs to try it.

(Mind you, even with YC's intake, it's likely you'd never see a statistically significant result either way. There's too many variables and not enough samples.)