Mickey, yes, mathematically 1 MOA at 100 is 1 MOA at 1000. In reality though, I typically don't see people running MOA groups at 1K - even the national champions. FWIW, my instructor for basic sniper was just put on the American team going to Bisley for the F-class T/R (tactical / restricted) world championship. He took 3rd place at the Carlos Hathcock memorial the year before he asked me to be his spotter.
Here's the deal - you and I both know that at 100 yards, a wind that gusts from 10 to 14 MPH at full value flatly doesn't matter. Hold and go. If you were shooting, and I was spotting - the target now at 600 instead of 100 - I'd dial you for a 10 MPH wind, try to give you the "fire - fire - fire" when the wind conditions looked right, with the call "favor" into the wind. I'd bet between the two of us, we'd get a headshot.
At 1K? I can't call the wind over 1000 yards to the nearest 1MPH. And I don't know those who can! We both know how much a miscalculation of 1 MPH wind at 1K will make, so suddenly we're not talking 1 MOA at 1K, when that error is added in. Will the stick do it? Sure. Will the ammo do it? Probably. Can we as people use that kind of accuracy at that range? Not often, and then it's either extreme skill or flatly luck. I was really proud of the trio of hits I made on the 900 yard iron maiden, a BARELY sub-MOA trio right in the chest. Could I do that EVERY time? Not hardly. 900 yards is a LOT of wind to call.
That's what I mean when I say that a rifle that does 1 MOA at 100 isn't a 1000 yard 1 MOA rifle. There's just too much that goes on over that much desert to let the bullet fly straight. At one point I couldn't get my shooter on at 1K, and I couldn't see the trace either! After 5 or 6 rounds, I gave up and went to the BIG scope - so I could see the trace. The bullets would have hit dead center THREE times - as in the wind call was great out to 600, but in the last 400 yards, the bullet cork-screwed due to the winds - first time I'd been able to see the wind move a bullet in what appeared to be 'up' as the trace went (I've had it unexplanably happen to me, just never seen the trace while it was doing so!).
Is a more accurate rifle more forgiving in such circumstances? Without a doubt. I'm just saying that when someone tells me they can put 'em all in 1" at 100, and therefore can hit 10" at 1K, I laugh.
I'm glad your Windrunner works great! We're in a different class of rifle now though. The instructor I was speaking of before had one, and he liked it. A fellow a few miles south of me got one, and I wasn't impressed - his wouldn't pick the rounds up out of the mag reliably. I wound up with an ArmaLite AR50
Your thoughts on an accurate spotters rifle put you squarely where I live - welcome ;D Really, I think we're more in agreement than not, it's just semantics.