NSFW content didn't show without an account for years. What's the difference between using the same account in the official app or on the website or third party apps?
Additionally one of the API changes which also goes is into effect is that they won't serve NSFW content on the paid API. So even if you pay you only get half of Reddit.
Hell, they could have banned all real NSFW content. Would have been a big deal, but wouldn’t have interfered with 3rd party apps or anything I use Reddit for.
Any NSFW stuff (due to laws, investments, advertisers, anything) had nothing to do with the API decision. They may have done them at the same time, but it wasn’t needed.
Additionally one of the API changes which also goes is into effect is that they won't serve NSFW content on the paid API. So even if you pay you only get half of Reddit.