I disagree. It clearly tells us _what_ is different, it just doesn't tell us _how_ it differs from case to case. So it's not a full explanation (which would,

I disagree. It clearly tells us _what_ is different, it just doesn't tell us _how_ it differs from case to case. So it's not a full explanation (which would, as you note, require a model of how it differs and, optimally, _why_) but it is a step towards a explanation, and not to be sneered at.