If the Extraction enchantment is applied before the Pierce enchantment, the ore block changes state before the Pierce enchantment gets to scan the body of the ore, and only a single block of ore is mined. If the Pierce enchantment is at the top of the tool's lore, the enchantments interact correctly.
If the Extraction enchantment is applied before the Pierce enchantment, the ore block changes state before the Pierce enchantment gets to scan the body of the ore, and only a single block of ore is mined. If the Pierce enchantment is at the top of the tool's lore, the enchantments interact correctly.