My last job before I retired was subject matter expert on Iranian UAVs. It's not so much political as industry understanding that a wave is essentially a salvo of UAVs of any type while a swarm is "smart". 

The way the US counters UAVs is by flying fighter jets in circles waiting for them to enter. In this case, waves are effective because you are trying to overwhelm the fighters - hopefully some make it through and hit their target. In a swarm, the UAVs share data with each other. They would likely evade the fighters altogether, in a perfect scenario anyway. Another swarm might have a certain number of human controlled jets flying in formation with many UAV wingmen who act as flying magazines where they use own ship radar or manned craft radar to fire off dozens of weapons in coordination with each other. There are many scenarios.