No they don't. It's not at all like when a string touches a pole piece.
If you know anything about Billy's playing, then you know he is one of the most aggressive players of all time. In fact, his entire career he looked for ways to avoid the exact sound you're talking about... from a strip of electrical tape to additional epoxy coating on top of a pickup, he is VERY aware of the unpleasant phenomenon about which you speak. These pickups are great in that regard. The metal cover is NOT a pole piece or part of the electrical signal chain in any way. When a string touches these pickups it sounds just like any other fully-covered (no exposed pole pieces) pickup. Of course, anything impacting a string in motion will change its sound and vibration pattern, so if that bothers you then yes, you should adjust your pickup. However, these do NOT make that horrible someone-whacked-a-sheet-of-metal-with-a-sledgehammer sound.
Hope that clears up any misinformation, and helps you make your decision.