It's sad to see that every free Reddit client is forced to be a browser nowadays.
Call me naive but in fact I always thought that's what the apps were using. One thing that took me by surprise in the whole fiasco was that the apps were actually using their own API keys -- I always thought I was just logged in to reddit in my own account. I figured it might be using some backend service for storing some app metadata but I didn't realize it was needing to communicate with reddit using the app developer's account on my behalf.
I can imagine however, that old.reddit.com scraping/parsing layers will pop up left and right as soon as that happens (and those in turn could be the final nail in the coffin for old.reddit.com)
They will, and go hard on it. Otherwise they are not backing up their problems and prior decisions.