That don't seem right, mine don't activate until they are almost on top of them ????
Check the replay again, did you use Another dragon, balloon or healer that triggered it and then died?
it will travel to the closest target then, minions are to small to trigger seeking air mines.
Can be a bug otherwise, I managed to trigger 1 CC troops with all my troops on the other side of the base, checked the replay 3 times.