The opposite of that is people who try to loosely project the variety of error modes their app has to http status codes. You then print out a table of http code

The opposite of that is people who try to loosely project the variety of error modes their app has to http status codes. You then print out a table of http code <-> actual meaning and try to outline ranges and messages you want to handle differently. On top of that, their backend may be down and you have to deal with bare reverse proxy statuses as well, which adds another dimension to that mess.