He’s got a point though. It’s not a direct answer to your question exactly but it’s quite relevant. If you currently run 7 days/week with one “long run” and hit 25 mpw, aren’t you doing like 3 miles six days of the week? So for one, dropping the long run and compressing that mileage into 6 days means your median/mode/typical daily distance increases. More importantly though is that he has you suddenly adding two quality days per week with basically no time to adjust to the added stimulus; adding a rest day could help you better recover from and absorb the new stimulus, and better your chances of running faster/more comfortably in those workouts each week rather than feeling worn down and flat (maybe even regressing) by week 3. Ya dig?