There is a big difference between CNS intensity accumulation leading to the need for recovery, and high intensity stimulus designed to bring about an adaption. Your 75% reps, in any volume, will not produce the same stimilus that a 95-100% Max V session or a 90-95% Speed End would. It might require the same recovery time, even more, but it will not provide the stimulus required to acquire the desired adaption. If Charlie ever wrote that multiple Extensive Tempo reps/sessions would accomplish the same adaptions as a 90-95% Speed End. or a 95-100% Max V session, I’ve never seen it. And there would be a lot of sub 10-11sec marathoners out there.
The same can be said in the gym. The whole TUT and Total Tonnage myths not withstanding, if you want a positive adaption in terms of increasing your strength, you will need to 1) perform an adequate number of reps/sets at near maximal intensity and/or 2) perform an adequate number of reps/sets at a submaximal intensity, preferably over 75%, using sets that bring you fairly close to failure (within 1-3 reps).