Re: Why the slant??
I don't know what the "official" Fender answer is, but I'd say you answered your own question...it changes the tone. Just try picking at various points along the string. You don't have to move far to hear the difference. The bridge/neck pickups are extreme examples, but I think it does change the sound.
On an interesting note, you may have seen slanted humbuckers (Van Halen, for example). I think he didn't do that for tone so much as to align the pole pieces of a Gibson width pickup to a strat spaced set of strings. The tone change on a humbucker would be less noticeable since the dual coils cover a greater amount of string space (length wise) in the first place.