The underlying requirement of providing source to users is firm, though. How else will a reverse proxy prominently make a statement to networked users?
> prominently offer all users interacting with it remotely through a computer network [...] an opportunity to receive the Corresponding Source
Yes, correct. If this is their best shot at a solution, it doesn't bode well for their interpretation of the AGPL allowing any UX-friendly version of this, let alone a normally functioning API Gateway.