This is where we differ. I don't need them to tell me the lore.
I develop that when I design the world or introduce the race. Might not use all three version, maybe this campaign is just the brutes.
Or....the brutes are the "ogres" of minotaur land, and the smaller ones are the smarter ones, who use the brutes in armies.
Sure, but you are homebrewing. If I'm going to provide feedback on a race, I need to know what they are going to do with it. When they put out a race they need to tell us how it fits into the official D&D multiverse, which is back to being a fundamental aspect of 5e products. For instance, if these are intended to be a different centaur species than the MM version, and they are found on such and so worlds, then I'm going to give very different feedback than if these are supposed to be the MM centaurs for PC usage.
I'm pretty sure in the Tweets referenced previously, Crawford does just that, by pointing to Medium Centaurs in pre-existing lore in certain settings: settings that we seem to be getting rule support in some future product, for which they are doing mechanical testing more than lore testing.
He shows us pictures. Does he point out official lore? Does this lore describe what would be our MM centaurs as being smaller than they were presented to us in 5e, or does this lore refer to a different centaur species that exists in some places (same as Krynn minotaurs vs. MM minotaurs)? Those are significantly different things.
Either:
1) There are two types of centaurs in some settings in the D&D Multiverse: the ones in the MM, and this new PC race type.
If this is the case, we need to know what worlds this is true in, and how it fits in the lore. It sounds new to me.
2) There is only one type of centaur, but the PC race write-up uses a different size category.
No lore changes really needed, but mechanically clunky and unsatisfying because it implies these are stats for playing a runt. And if that is the case, they need to explain you a playing a runt.