"More substantive" technically, but really it's just a few short sentences that boil down to "some people think strategic default is morally questionable, others do not." I would be interested in a more substantive exploration of the issues though. In my perspective as someone who hasn't thought about it too much: Morally because strategic defaults (which contain an intent element) end up being paid for by other people not parties to the transactions, it brings it into a morally questionable area.
Breaking a contract by itself isn't morally questionable, but if you perhaps contract to provide PPE for hospitals in a pandemic, and then choose to not provide that PPE for no reason other than you don't want to (or it's more profitable to just not fulfill the contract) causing people not a party to the contract to be harmed, that's morally questionable. It's a very fact specific inquiry.
Wikipedia has a more-substantive bit on the ethics:
https://en.wikipedia.org/wiki/Strategic_default#Ethical_issu...