grey areas...
The app was not approoved containing 17+ content, rated that way or not. It was advertised to everyone who previously downloaded it as containing only underwear clad models. 17+ or not, the downloaded had a given expectation of what to expect, and by the company changing the content post-approval, without updating the app version or requiring a re-download to access the new racier content, they did in fact violate Apple's policy as it;s possib le (though unlikely) that existing app owners might have been offended. (I actually have an uncle who loves women in lingere, but speaks against playboy and nudity, he might have been offended).
If they posted an updated version, enabled a way to seperate nude from noon-nude content through the app, set nude as defaulted to off, and tied it in to the rating system more directly, allowing those still interested in the non-nude features to continue use without accessing nude content, then this might have gone down differently...
Apple has ALLWAYS been fishy about externally linked content... The devs knew they were skating on questionable ice. They should have partnered more directly with Apple on this.