Earlier quoted context omitted.
When did we stop building software for the "Power User" persona? I don't disagree that there are some (many?) people who start screaming and running in circles when they see an error code, but not every user is like that. You don't have to be a dev to care any the distinction between a system doing its job and silently failing. Why not have some indication that there's smoke coming out from the engine?
This sounds like inconsequential quibbling over terminology. There's nothing stopping a browser power user from opening up dev tools to look at error codes.
In other words, as a power user, I want to know if the site has a "You problem", and the only explanation I fully accept for why the modern web doesn't notify users about website errors is that it allows companies to save on QA costs.