When I tried to drop a stack of 64 items by pressing and holding 'Q', from my inventory, I could only collect 13 that were on the ground; In survival if you drop 64 blocks/items, you can collect all of them back.

Steps to reproduce:

1.  Get 64 of any item in the creative inventory{}
2. Without leaving the inventory, press and hold 'Q' on the item to drop it
3. Exit the inventory, try to pick up the items and only get 13.