I applied it to a random low level shoulder item and wore it while going around nuking everything in Broken Isle. Not a single “Pile of Pet Goodies” dropped but I do remember getting quite a few a few years ago. I am trying to quickly farm shiny pet charm to get that 1,000 charm toy.
The tooltip only stated it can be applied to max level 60 item, nothing else. So it should still work with a random low level shoulder item.
Incidentally, I first tried the boon on a level 60 shoulder, got an error message too high. I used a lower level shoulder to get the boon applied. I think the tooltip needs to be updated for correct level that can be used.