nah, those people would attempt to place in cube. cube was full, so they’d drop the item and make room. then it would break the chronicle id.
or that clown with the tyrael post who looted to cube, then moved to shared stash, then left and went to a new game before identifying.
I thought it was the "pickup on cursor, cube full, drop item" at first as well, but that doesn't seem to be the case. It really is just as simple as having it on your cursor the first time you pick it up, but as for why it's rare, there must be another unknown step that triggers it.
I told people the same thing as you, but it seems that's not the case in every single time it's been triggered.