smps shield winding
FvM,
i agree entirely with your views on the need for synchronizing SMPS's in parallel.
Take your car...........if all your lights are LED lights, you WILL find that the direction_indicators, brake lights , reverse lights and tail lights are ALL done with LINEAR REGULATORS .
This is because having these done with separate SMPS's would mean a bad EMC situation caused by the close-together SMPS's interfereing with one another.
SMPS's do get used in some cases but if so, then the four SMPS's are done with staggered synchronozation, in other words the four clocks of each of the four SMPS is phased apart by 90 degrees to reduce bad EMC effects.
....you then have the difficulty that the synchronizing clock is often at 500KHz plus and this is an awkward signal to easily route around without very good layout.