minecraft:mined statistic depends on whether the tool can harvest the block

When mined with a golden pickaxe, a copper/gold/iron...ect ore block will not update a "minecraft.mined:minecraft.copper_ore objective", even though it is the preferred tool class. It only updates when loot is generated.
There is no reliable way to detect most ores being mined with lower tier tools, since altering the loot table to enable the lower tier, is still being overridden by whether or not it can generate loot by default.