You know, this isn't Unreal Engine, but when I tried playing Doom 2016 before, I swear the FOV felt really weird for being set to 90. I have no idea if that's right, but it did make me wonder whether some engines might be doing some kind of conversion. Like, instead of setting vertical FOV directly, you set the 4:3 horizontal FOV, and then they take the 4:3 vertical FOV and use that as the actual FOV for all aspect ratios, or something. I haven't played either Zeno Clash, but it might be something like that...