As a lay person, who for some reason reads WB economist blogs, I think I managed to understand this. And it seems to me that even the abstract, not just the blog, is misleading the reader by focusing initially on T-S, when in fact, as the abstract then goes on to show, S-C is negative, making T-S not something we should be considering first, but should be first considering T-C. The abstract's main points should be T-C is positive only for assets and S-C is negative.
But S-C being negative seems to me is hugely alarming. This is where I'd like more explanation, if you'll indulge non-technical readers, because I don't understand why you seem to be concerned mostly about 'sustained treatment effects' or T-C even though it seems S-C is negative. If S-C is negative, doesn't it suggest that T-C could be coming at the expense of S, meaning T-C can't be our primary concern?