The fact that you can define expectations for capabilities the producer may not even have yet also better fits into a workflow where the producing service is still being (or has yet to be) developed.
They mean with pact you can but not with pacto? Can't you do it with either? Or they mean if you have to rebuild spec every time, it's not going to work but with pacto you build only once?
I like that pact is also testing the mocks that consumer is using.
