I actually agree with you wholeheartedly on this, there is an issue with regards to company line vs personal inclination, but that's important to have here, because it's the exact problem that exists between content and moderators; each moderator is applying their own interpretation of a somewhat subjective rule to how they monitor content.
I'm not saying they're all totally biased and subjective, of course, simply that the grey line exists explicitly because of that personal bias; it can't be removed, but I think that it should be managed as well as it can. It's one of the reasons I consider an explicit content alert to be a great part of a forum community, even if you do want to put hard rules against graphic nudity or sex scenes in place, having an explicit content system is a great way of managing personal bias; do you think it's a possible rule-breaker, but can see why it may be acceptable to others? mark it as explicit content and move on. Is someone doing it a lot? ask them to re-read the T+Cs and advise them to take more care to use those content markers in future on their posts. If necessary, escalate and treat as any other ASB online
Riot are in a difficult position in appealing to the mass gaming market, both also being considered a relatively family-friendly game. I'm not saying 4 year olds should be playing hardcore plat 1, but that parents want to know their teenagers or pre-teens can play without it being too explicit, and that's a good thing for the game. But balancing that with their adult clientele makes it a challenge, and I think having a black-and-white system (shown or removed) for grey area content can sometimes cause more harm than good.