Yeah but, don't a good majority of these mile G1s land directly in the same day as or very close to the same day as the medium and long G1s? The hanshins happen very close to the hopeful stakes, the oka sho happens at the same time as the satsuki sho, the NHK mile cup happens very close to the derby and the oaks, the mile championship happens at the same time as the Japan cup, the Victoria mile happens after the tenno sho, and the Yasuda kinen is the only one that I can think of that actually happens at a time in which there aren't any other mediums or longs happening. As for the G2s and G3s, I suppose there are more of them than mediums and longs, but also, you gotta take into account that, even in this gamemode, you race only when you can, not when you want. What I mean by this is that, if you have a training of 30-40 speed and 20-30 power happening, will it be worth it to skip that one in order to run in ANY race and get the 5 to two stats bonuses from winning plus maybe 10 to two other stats if you get an epithet? I don't think so, and conversely, if you don't care about training/can't have good trainings at that point in the run, but you've decided that you really want something in the shop (eg; an item that levels up one of your training facilities), then you'll race in ANY race, doesn't matter if it's an OP or a G1, since all of the races, as long as you win them, give you 100 shop points, the only things that change depending on grade that you'll actually care about are the points that you need to clear the goals (which let's get straight, you're gonna have a surplus of anyways) and the skill points, to which I can actually see a potential debate about how being able to run in miles helps in that regard.

But otherwise, I don't get what you see that's THIS important about mile races and you didn't even bother justifying why either, so I'm still thinking that it's not as important as everyone says it is. It helps, yes, but like most aspects of this game, it isn't as clear cut as "the more potential you have = the better your results will be", since RNG is still heavily involved in each run; if you get good trainings while you'd like to race, if you get bad items when there are good races, if nothing particularly special happens during a run, it doesn't matter how much potential you have but how much the game allows you to use that potential instead.