So the consensus idea is that if one gets into Harvard/Princeton/Berkeley, it doesn't make any sense (unless there's some really jarring reason why you don't want to go to one of those schools), to turn it down for other programs in the Top10/15 that may seem now to have a better fit for a highly specific version of your research interests? Because that highly specific version will likely change?
Yep. That about sums it up. Particularly Princeton and Harvard. Berkeley is sometimes turned down because of potential funding issues, which Princeton and Harvard will not have. But yes, I think it'd be unwise to turn down any of those schools for other schools in the top 10/15. Yes, indeed.