Hezbollah is not a mobile device distribution organization. From my understanding they bought these to avoid Israeli tracking for their own people. No civilian doctor would use these pagers but there are medics working for Hezbollah like any militia/army.
Due to the nature of the devices I doubt it's physically possible to verify every explosion. Just like you can't verify it with a bomb or even a bullet. It's tragic that civilians are hurt but that would happen in any case when there's a war.
Hezbollah themselves bootstrapped a phone in the past. They also recently fired on a football field and killed 12 children. Then they hide in tunnels while leaving the general populace of Lebanon to deal with the wrath of the war that they started while they keep shelling the northern part of Israel. These parts of Israel and Lebanon are abandoned now because of their war. For once, they actually got some consequences for their own actions.
Was it 100% perfect and surgical?
Hell no. Nothing ever is, that's fantasy land. But it's about the closest thing that you can get to an ideal attack in these specific circumstances. The fact that the attack produced less than 1% in casualties shows the concern for collateral damage in this situation.