Yes but point is about the immediacy of the coming of the son of man. Jesus is telling them its a difficult mission. Some will be killed and others tortured. And this mission won’t be completed until the son of man returns – ie it is impossible to complete the cities without the coming of the son of man.

And “whoever endures to the end will be saved”. Matthew 10:32.

It is not the case that its a simple mission and the son of man will return sooner than they can walk through Israel.