Why there are no new Nikkor 1.2 lenses

According to the Internet (so it must be true 😀) that the reason why Nikon can’t produce their latest Nikkor lenses at f1.2 is because of a technical factor.

Someone once told me it was because of the flange but I have read elsewhere it is because of the difference in the size of the mounts. As you can see from above, the Nikon (on the left) is much smaller than the Canon.

Is this the reason that Nikon can only get to f1.4 and no more?

Also according to the Internet the difference between f1.4 and f1.2 is not big and that Canon only do it so that Canon fans can play lens Top Trumps with Nikon fans.

Whatever the reason, it would be nice to have some f1.2 glass in my bag.