1. They have a policy of marking apps as NSFW if using them has a high probability of loading NSFW content onto the device. We can't easily rule this out. It's a small project so they have to be reserved about compliance issues because they don't have the resources to defend against expensive litigation and they could just be exercising an abundance of caution.
2. They're trolling Republicans with malicious compliance. They don't like the laws being enacted, they know the people enacting them like the Bible, so they apply the policy in the way which is maximally adversarial to the opponents imposing it on them. "If you don't like the consequences of your law then feel free to repeal it."
Which one of these is even objectionable? It seems like you want that if they're doing the second one they should admit to it, but in that case they're just maintaining kayfabe. The trolling is more effective when it's ambiguous. It's obvious that it could be that. If the message is to invite their opponents to go eat sand then it's not being lost in translation. But making that explicit only makes it easier to dismiss them as antagonists, or retaliate against them for being overtly defiant.
Whereas if they play it straight, what is someone going to say? That it shouldn't apply to this, right? Okay, then we need to pin down the rules for how exceptions work. Exceptions that could then be applied to other things. Which is to their advantage to have their opponents doing in this context because then they want the exceptions to be broad and reasonable instead of not caring if someone else is getting screwed by them.