Your reverse proxy also would suffer the other shortcomings of proxying to our service described here, @jclusso : [Support Guide] Why not proxy to Netlify?
We’ll be having our retrospective call tomorrow where we discuss the future of our network layout and we’ll publish a root cause analysis describing the measures we’re taking to protect you going forward in it. I’ll link that here for your consideration.
As to why we weren’t configured that way today, I can’t speak to that since it wasn’t my decision, but I suspect that RCA will shed some light on the history and show a future more compatible with your wishes.