Yeah, the difference is more of a cosmetic one than anything. I think it was most likely more of a marketing thing that a functional design change. I've never really done an objective comparison between a traditional spaced pickup and its F-spaced counterpart, but I have had many pickups with spacings that were mismatched to the guitar, and I've never noticed any tone or volume "dropouts" between the strings and no issues when bending like people used to say a lot when it came to this topic. I think that whole concept, if not an entirely made up marketing scheme that shaped the entire aftermarket pickup industry, was more theoretical than a pragmatic one considering that the magnetic field on a humbucker is generally cylindrical shape that surrounds the entire pickup in all directions and not 6 small, precise magnetic fields that are perfectly aligned to the strings. If there is a difference, you are most likely only going to hear it when playing with a clean, uncompressed sound. The second you start playing high gain and that compression sets in, I am about 99% sure that the average player will not be able to hear a discernible difference.