This is definitely how I felt as well. The discussion is kind of circular, "You need a clock because doing things without a clock doesn't fit well into a clocked paradigm."
It's not an argument against clockless design, but an observation on the limitations of doing everything in a single clock tick of an already clocked chip.
We can surely build a circuit without any clock, but what challenges do we run into? How does imposing discrete clock steps help? What exactly is a clock? I would have liked to see the discussion drop a level or two of abstraction to EE or something.
Right, so what the author hinted at, but never really said, is that without a clock it is difficult to prevent spurious intermediate values output by circuits from having unwanted effects; for example, unbalanced combinational circuits typically shift between multiple intermediate values as the signals propagate through. Such hazards are normally avoided, though I can imagine such hazards might potentially contain information that could have adaptive advantage (in evolutionarily derived circuitry)
I am guessing it's because the clock ensures that the delay is always the same for all components but that also means a single clock cycle must takes as long as the slowest component. With an asynchronous design every component has a different delay but you still have to ensure that all input signals to a component arrive at roughly the same time.
