Stacked Items In Villager Trades

What I expected to happen was...:
That the Items don't stack

What actually happened was...:
The Unstackabille Items are now stacked!

Steps to Reproduce:

Video: https://youtu.be/0q3dM4ch_2A
1. Spawn a Villager witch cutstom Trades like:

/summon villager ~ ~ ~ {NoAI:1b,VillagerData:

{level:1,profession:"minecraft:armorer",type:"minecraft:desert"}

,Offers:{Recipes:[{buy:

{id:"minecraft:diamond_pickaxe",Count:1b}

,sell:{id:"minecraft:end_stone",Count:1b}}]}}

2. Put in your Inventory more than 1 unstackabille Item (Here: diamond_pickaxe)
3. Click on the trade (were all the Trades are in a list)

4. Your Items are now stacked in the Villager trade Slot

5. Simply take them out!