I'd agree with Ballad of Caius on this one. The modern, trendy fantasy story is dark, gritty, edgy. Blood. Death. Sex. Shocking twists. Square is probably looking at that and going "that will spice up Final Fantasy".I figured this game would get a Mature rating after seeing the blood. I wonder why they decided to go in a more gritty direction for a mainline title.
And I'm playing through the MSQ of FFXIV, so it actually makes a lot of sense to me that Yoshi P would make XVI extra dark. FFXIV itself is very dark in places, with executions, almost an entire group slaughtered in their secret base, a slightly comedic but dark scene of an NPC party who lost a member and that deceased person's soon-to-be wife and healer carrying his head in her inventory (wtf), a boss with a backstory where she gathered maidens to kill them and use their blood to gain immortality.... The list goes on. There are a number of quests requiring you to carry a corpse or two (sometimes a bunch) to places for burial.
In all honesty, Final Fantasy had been this dark before. The only thing making XIV not M is the lack of on-screen blood, probably only do lack of graphical capability. With XVI though that isn't an issue, so... We have it.