Really strange. Horizontal (16:9) also does not affect my sensitivity scalings here. If you figure out what is causing it, let me know.
I can confidently say that I have disabled UE4's "Enable FOVScaling" option in the Project Settings of the game (which is how the engine normally handles sensitivity scaling as FOV changes). Furthermore, none of my my sensitivity scales take the FOV setting as an input, although that does make my Paladins scale inaccurate.
Side note: I've been meaning to remove/disable that one for a while due to the ambiguity of scaling sensitivity with FOV along with differing FOV scales and aspect ratios. For example, if a user sets his FOV scale to clamped horizontal and 103 with Paladins sens, that's all well and good, but what if he uses Horizontal (4:3)? Or what if he uses Vertical? Should I be taking the FOV number he entered, or should I be determining the actual horizontal FOV and scaling by that? I'd rather just... not have it be an option to avoid that confusion.