Decorated pots drop their item when /setblock or /fill is used even when replace is selected.

Examples: (if the pots located at 1 64 1)

/setblock 1 64 1 minecraft:air replace

/fill 1 64 1 1 64 1 minecraft:air replace

You will noticed the pot is still drop also when using destroy it should probably drop bricks instead.

This is not normal no other block drops itself with replace.