final fantasy xv pocket edition is out

That's not what the ratings mean at all. It stands for Parental Guidance.

Both PGs are for movies and TV only; Motion picture media is rated by the Motion Picture Association of America (MPAA) and has the following ratings:
G, for General Audiences, meaning there isn't anything anyone would find offensive. This matches to E, for Everyone, in the ESRB system. PG, for Parental Guidance, which means it has some content that more conservative parents may find troublesome for younger children, matches to Everyone 10+ in the ESRB system. PG13 matches to Teen in the ESRB system, with both of them being targeted at 13+. R, for Restricted, matches to M, for Mature, and both systems have an "Adults Only" rating at 18+.

In short, our systems match to one another (which admittedly does make their differing terminology rather unnecessary), and in turn, to PEGI; that is, other than the difference in perceptions of violence and sexual content, and the fact that we target 13 and 17 instead of 12 and 16 on ages. I wouldn't say our systems are terrible (given that they differ only in nuance from PEGI), but PEGI does strike me as far more reasonable in its considerations [though that's really more of a cultural difference between American and the (less infatuated with violence, less hung up on nudity) parts of the world, than it is a difference in the systems themselves].

Moreover, most of the terms mean little on their own; In both games and films, the only "enforcement" comes in at Restricted/Mature and Adults Only. For anything lower, the ratings only serve to inform parents of the content involved, not to set standards for or put expectations on retailers. Even as far as retailers, internal policy dictates their selling habits on R/M content rather than any sort of legal risk, and it's not uncommon (in my experiences) for cinemas and retailers to not enforce Restricted/Mature requirements of having an accompanying or authorizing adult, so long as you're not overtly underage.

Adults Only, on the other hand, can actually get retailers in trouble (for both games or film) if they sell to minors (due to them falling under pornography laws)- though that restriction on selling hasn't stopped retail stores from displaying adult films in very visible places (it used to be standard practice to stock them directly next to Anime, before Anime got popular and better understood by retailers -.-). Game stores, on the other hand, have a long-established practice of refusing to stock adult games altogether, which is why we'll likely never see a game with explicit sexual content sold in the states, regardless of the narrative value.

On the other hand, fade-to-black scenes like those in God of War and Witcher have become well-established as now being acceptable under M alone (which is, at least, is a step up from the 'anyone being topless is M and, oh gods, vague sex references? No, that's Adults Only for sure' standard that [in conjunction with the practice of stores not stocking AO games] all-but-prevented games from including such elements in the past), meaning we don't really need anything explicit to drive narrative device.
As such, eroge visual novels are really the only notable style of games [that in any way use sex as narrative devices] affected by the restriction- and given that those are currently exclusively imported by companies like JAST [that is, companies which on the whole are focused on digital sales], they're presumably not much affected by the restriction.