armadillo_shed.json does not overwrite default drop (1.21.4)

data/minecraft/loot_table/gameplay/armadillo_shed.json does not overwrite the drop for brushing an armadillo. Given identical file contents, with the only change being "minecraft:armadillo_scute" replaced with "minecraft:leather", the armadillo still drops armadillo scutes when the datapack is applied and the armadillo is brushed. am i missing a step or is this impossible?