I don't know, maybe I'm missing something but it seems kind of stupid. "Let's broadcast this at an insane hour when no one is going to watch this to avoid spoilers. Then let's re-broadcast this at a more appropriate time when everyone's watching TV."
As long as the broadcast on the same day, there's a slim chance of people looking up spoilers anyway. Yes, I'll admit, an hour before the season 7 episodes aired I'd go online and look up spoilers from the UK anyway, but that was only because I really am impatient. I doubt everyone is that impatient, even with a landmark episode like this.