When using a repeat command block to set any hotbar slot to any amount of blocks with the following command for example:

/item replace entity @p hotbar.0 with minecraft:light_blue_wool 10

The behaviour I expected would be that the blocks in my hotbar should continuously be replaced by the command. However when placing the blocks the amount of blocks in your hotbar goes down and vanishes when getting to 0 but you can still keep placing the blocks.

Example + steps to reproduce: https://youtu.be/UpT1nJzOsZU