I don't know in which context the writer is writing, I'm a developer and have been mostly working on startup-style projects. If you fail, you don't make a buck, the product does not work or does not sell. The downside is the lost time and money.
I have also known couple of startups, which have had really good engineers who have invested lots to testing, maintainability etc. In the end however the business hasn't succeeded selling the product, and all that investment was worth essentially nothing.
Or destroys the users' financial well-being: software they use to run their small business, or invest their retirement?
https://en.wikipedia.org/wiki/MIM-104_Patriot#Failure_at_Dha...
Whether or not this can be attributed to technical debt, I don't know. But it is an instance of a software failure that resulted in death.
I suppose net across the system, you could inflict more downside to others exposed to your default, but it's not unlimited unless you can wipe out the entire planetary economy (financial and non financial) with your bet.
Don't take it so literally; it's just a short-selling simile.
A bit like learning to fish is better than giving a guy a fish.