The issue was confirmed with two separate MagSafe chargers and three or four separate AC/DC chargers. The lab test in the post was done using laboratory DC power supply powering a DC to USB converter.
Also if the interference didn't come from the disc side of charger then the issue wouldn't be resolved with ferrite bead on that end. If the issue was on the USB connector side then the bead should be placed there.
Also if the interference didn't come from the disc side of charger then the issue wouldn't be resolved with ferrite bead on that end. If the issue was on the USB connector side then the bead should be placed there.