I bought some eggs for a new seller earlier this month. 2 of the 12 arrived broken. I put the others in the incubator and a week later noticed the stink. Found the bad egg. The next day the stink was back. I found another bad egg and removed it. And again two days later. All seemed fine this morning, no smell. But one of the eggs had come apart like a cheap tire, only messier.
So I'd say you were lucky you got it out in time. If you look at your picture, the long, clean cracks are indicitive of the egg splitting from internal pressure. If you get those at any point it's past time to pitch the egg, whether or not it smells bad. Pipping and unzipping both not only look much different but you'll hear the bird moving and chirping with them.
Now I'm going to go find the other six eggs from that batch and toss them. Because I'm pretty sure someone sold me hatching eggs she collected from her incubator, not her nesting boxes.