18G,
I read about these in Alex Kimble's book "Think Like a Bird", even in the 50's it seems to be regarded as the old way of doing things. Other than good practice, I don't think I really understand the logic. If anything the engine is less likely to fail at a low power setting during final when compared to any other part of the circuit (carb ice discussions to one side for the moment, that is down to equipment and technique).
Are you suggesting that an aircraft should be in glide range of the runway from any point in the circuit? If so I don't suppose that would be very practical for many airfields. with all the traffic and noice restrictions we have.