I think you make some valid points.
I find the information you looked up about your old program interesting, particularly that 30-40% come from international schools. I suspected there were several, but that is quite a lot. So roughly 35-45% come from non-Ivy/non-international schools. I'm not sure I would consider Cal Tech to be a "random" school as we've all heard of it, and I think everyone is aware that (even small) private schools usually fair well. I think what is more interesting (and perhaps more relevant to those of us who have been voicing concerns about the importance of undergrad) is the percent of students coming from small state schools. This wouldn't be schools like the University of X, X State University, or even (in some cases) Northern X University (I'm thinking of Northern Illinois which people have heard of), but schools like University of X at (insert random, small location...this obviously doesn't apply to the extensive California system). Seeing how many students come from these sorts of schools (state ones that we've never heard of) would be worthwile.
To your second point, would you not agree that more often than not both kids (the one from Harvard and from Western Michigan) with the 3.8 will have excellent recs? Who would the school pick in that, more likely, case? I would think that in most cases kids would have similar GREs, GPAs, support in recs, etc. In the event that they didn't, however, I agree that the school would be less likely to pick based on undergrad. But when all else is roughly equal, who could blame them?