How exactly does cross-chaining accelerate wear? I've heard all over that cross-chaining "wears your drivetrain out faster". I must admit I'm not 100% convinced that this is true, because I can't see a scientific basis for it.

Could I get an explination of exactly how and why cross-chaining wears out your chain/cassette/chainrings?
When the chain is bent sideways, the load at links is concentrated on one end of the pin and single side plate while the link is turned. This is supposed to wear that side of the link faster. Once the link is worn asymmetric, even straight chainline will concentrate load on the less worn side.

No, I don't know if there are any actual measurements on this.