Do I need to pickpocket 50 different people or 50 Items for Skyrim's 'Thief' achievement?

In Skyrim to get the trophy/achievement "Thief", in which you have to pick 50 locks and 50 pockets, do you have to pick 50 different people's pockets, or just 50 items from pockets?

Based off one of the solutions on this site:

You can place each key individually, and when you steal them back they all come at once. So that's 5 pickpockets from one target.

This person placed keys in people's pockets and then took them back over and over. This denotes that it's 50 items pickpocketed and not 50 different people.

If he got caught, he'd reloaded a save. He also saved after taking his keys back each time as a precaution.

The Wiki also states:

While the description says to pick fifty pockets, the requirement is to steal fifty different items through the use of pickpocketing. Stacked items will not count as multiple items (e.g. stealing a stack of twelve steel arrows still counts as one stolen item).

It appears that stacking items like the person did in the linked guide may not be true, but it still seems like you have to pickpocket 50 items.