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 f

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)