When you run 1x, aren't you basically force to cross chain?
One key difference is the design of the chainring. A traditional ring is made to allow shifting, which means there’s specially shaped teeth and protrusions that will pick up the chain and help lift it in to the next gear.
Cross chaining with traditional rings will put the chain in the angular region where it ‘thinks’ you want to shift (ie. these mechanisms will start hitting the chain plates).
On a 1x system a narrow wide ring is typically used, or a similar device, that meshes more completely with the whole chain link. Since it doesn’t have to worry about shifting, it’s only worried about retention, so it can ease the chain into a consistent position from a wide variety of angles.
As for the rear derailleur, they’re designed to rectify the angle as well, with SRAM opting for a more eccentric pulley position relative to the pivot, and Shimano using differently shaped parallelograms. Both these systems keep the pulley a consistent distance away from the sprockets, so the whole system can accommodate wider chain angles.
If the single chainring was located in either the 2x large or small ring positions, to either side of the nominal chain-line that would in fact be the case. It isn't though, it's positioned on the chain-line so it lines up with the center of the cassette - pretty much like the middle ring on a 3x system.