Not really, no. The only thing a low-level NPC has in common with a minion is that they can die from one attack. In almost every way that matters, a low-level NPC is different. For one thing, even if they have 4hp, they can survive the little bumps and bruises that we pick up in our daily lives. For another thing, their relative durability is based on factors that actually exist within the game world, rather than a meta-game descriptor of their relative importance to the narrative.
Minions work fairly well, in the context where many of them are facing off against the PCs in combat. The further you take them away from that context, the less sense they make.
As I said, the weakest possible PC has like 13hp, and a level 1 goblin has 25. The way these miners were described, they should have been tougher than that. They may even have been dwarves. Even if they were level 1 standard NPCs, their numbers should have been enough to turn the tide of combat; but since they had an invisible 'minion' flag, they all died meaningless deaths.
There was absolutely no way, whatsoever, for our characters to know that they were minions. If they were minions, it's improbable that they would have survived so long in an open mine. They would have stubbed a toe, or been stung by a bee, or fallen victim to any of a million other things that deal the minimum possible damage. The fact that they were still alive should have been proof enough that they weren't minions.
Of course, the same could be said of any minion. A level 21 giant minion could not feasibly have survived to adulthood without taking a point of damage at some point along the way. Treating minions as an objective aspect of a persistent reality is an exercise in futility.