I think their target audience isn't the typical HN reader, but the rest of the industry, where multiple staging environments are still a common thing (including my current employer).

The biggest issue we had with preview/review environments was resources not being cleaned up properly after destroying the environment (along with the associated costs), but that was more an indictment of our IaC code than anything else. It also didn't eliminate staged environments for things like the non-standard DB that we were using. As long as the changes on the DB side were net-new, it wasn't really an issue, though.