Yeah, I don't remember where I read that at. When I first heard about it, there was a lot of chatter about it in a few other forums. AR15.com was one the forums that was popping up in my search. So I repeated what I read on the there.
Now actually thinking about it, Winchester doesn't make AR's but they do sell bolt actions. So it makes sense.
But I dont think it will be too long before it's available in some sort of AR.
The thing nearly everyone is missing is that the .350 Legend was announced by Winchester Ammunition which while under the same overall umbrella, is a different company than Winchester Repeating Arms. Winchester Repeating Arms will make an XPR in .350 Legend(I would bet we will see a Browning in this chambering soon as well since they are also under the same umbrella) but Winchester Ammo is promoting the round precisely because it will be opened up to other firearms manufacturers(read AR manufacturers) so they can sell plenty ammo.