Are specialty mines broken?

I don't know if I was the only person who suggested it for SE4, but Aaron included specialty mines in SE5 and back before I was forced into SE5 hiatus for a while I thought they were working. But I am playing again and I'm seeing the old buggy behavior. Can anybody shed light on this or confirm the bug?

Suppose I have a minefield with zillions of Ion mines. Suppose an enemy ship enters the minefield. The correct behavior would be that some number of mines would detonate and destroy all the engines of the ship, leaving the rest of the mines lurking.

The behavior I'm seeing is that all zillion mines, valiantly attempting to destroy that ship, throw themselves on it and blow every last dust mote that's left of its engines to separate quarks, then try to blow up the quarks.

I.E., the first ship to come along will use up all the mines as they vainly try to destroy the engines it no longer has.