Throwing a 404 response from loader causes "Handling response" message + error boundary doesn't work

[nboliver-ventureweb]

When throwing a 404 response from a loader per the Remix docs,
a "Handling response" message shows.

Tried adding a custom error boundary after finding this issue: #597 (comment), but it does not seem like there's a way to make that work based on @paulomarg 's comments.

What is the recommended process for custom error boundaries in this situation?