I believe you are correct about beginning runners having more of a benefit from a jump in VO2 max.
On energy systems: It is true that all non-aerobic (anaerobic) activity puts an athlete in an "oxygen debt??? which is made up by heavy breathing at the end of an activity. For example if an athlete were to run a 12 sec 100m sprint his body would require app. 6L of oxygen for total aerobic respiration. However the VO2 max during that 12 sec is 1.2L, and would incur 4.8L debt, requiring one to replenish that oxygen through heavy breathing. As he becomes better conditioned, his VO2 (and, of course, anaerobic threshold) improves and his oxygen debt lowers.
In fact most athletes have a 10% greater VO2 max than the sedentary person does, and marathoners have a 45% higher VO2 max. This is one reason why an elite distance runner can do a workout like 16x200m in 24s without breathing as hard as a short sprinter trying to attempt the same workout.
Hope it wasn't too wordy, just wanted to clarify the value of VO2 -assuming there is one of course 🙄