digital logic - Edge triggering seems to me leaving every circuit in an inconsistent state?

I was informed on this forum that edge triggering could be a solution for multiple propagation in a circuit with feedback (the output wired back to the input).

But to me edge triggering seems to leave a circuit in a completely inconsistent state. Look at this one (one-element JK flip flop ripple counter).

Let the clock input be edge-triggering signal and look at the first NAND field at J when all inputs at J are high but the clock. At the moment the clock gets high the propagation starts. The edge lasts for a nanosecond so it will probably end before the value propagates through the NAND. Anyway, a nanosecond-long low signal will travel through the output of the first NAND, preceded and followed by long intervals of high signal. That composition will get to the the second upper NAND and the NAND will change values accordingly, further branch-wired to another NAND plus an input, and it all looks like a great example of an inconsistent state of a circuit to me - who knows what is going to happen there?

I don't get properly something about edge triggering. What is that? Thank you for the time!