Actually... that's something I have doubts about. It isn't all NSFW subs, just the porn ones... and how many people actually comment on porn subs, instead of just scrolling and... well, "consuming" it?
My guess is users of porn subs will use the official app and not care about it.
The point of those porn subs (generally) is to drive engagement to paid sites. If the content creators find that there is less traffic from Reddit, they're going to stop posting there, regardless of the app.