[OhMeadhbh]

It's high single digits of seconds away. But I think your point still stands. Burke turns his head to look at the rocket, so you can't see his lips aren't moving. His voice-ove that includes "planets or peking" is surely an edit and yes, you can hear the rumble of a rocket (maybe not even the same rocket.)

However, I don't think people were praising this shot for it's audio editing. I wouldn't be surprised if Burke re-recorded it and they dubbed it over the video. I think they're saying this is an amazing shot because the timing seems to be pretty good... He points at the rocket and about a quarter or half of a second later it ignites. This comes at the end of a 10-ish second sequence. Pretty good timing. Unlike other shots in popular media up to this time it would have been difficult to try to do a second time (though I guess they could have tried again at the Voyager 1 launch a couple weeks later.)