not sure where the 3% metric is coming from but from what I understand, a big hit to "no 3rd party apps" is moderation tools - it'll make the larger subs more difficult to moderate - and will end up costing reddit $$$$ when the unpaid mods quit over it
Only 3% of Reddit users use third-party apps. This was such a weird hill to die on and it's not going to make them suddenly profitable. Models of monetization that rely on advertising just don't work. Adding a few thousand users to the list of people who see them isn't going to suddenly make it so.
save