True knot in umbilical cord

[Smoke Jaguar]

I figured it was because he was so small that he had enough room to pull that kind of manoeuvre, and he was so small because he had one channel of nutrients rather than the two arteries from the placenta. None of this was picked up in earlier scans and the pregnancy was otherwise normal until that point when he wanted out a couple of weeks sooner.
I've heard of knots before, but can't remember from whom - not common. I'm guessing the flip flopping gets the cord into a knot and then when the baby is starting to position and engage it tightens the knot, so closer to the end? In layman's terms!
ETA: posted at the same time, Arcadia! Yes, my cousin was induced, in the end, because they didn't know what state the baby was in, except that his heart rate had dropped below what they were comfortable with in the ward, once she'd transferred.