When you drop an item manually, the origin of the item is correctly the person who threw it - however, when you break a tile and it drops items, the origin of those items is not the player (or entity if it's still alive, such as a ghast) who broke the block.

—

Simple setup: 

Run

execute as @e[type=item,limit=1] on origin run say @s

in a repeating command block, and break any block with a tool that causes it to drop an item, and the command will not say anything.

If you then throw an item, it works as intended and says the player's name.

I apologise if this is actually intended behaviour and this request is unnecessary, but it seems like it isn't intended.