20 years ago I followed the macrumors WWDC feed because streaming was broken (for bandwidth / my connection / quicktime reasons). Today, I will follow the macrumors WWDC feed because streaming is broken (for artistic direction reasons). The more things change, the more they stay the same.
Same behavior for me, I assume that they're going to let the thing play out and then you'll be able to replay once the event finishes. Not sure why this has changed from other livestreams.