Again that never happened, you're making it up. It happened in two spots in the game.
Grenade spam happened all the time in WaW on higher difficulties. It was ridiculous.
Re-spawning, did happen, but there was a limit to how many enemies would spawn in total, so if you did hang around long enough you could eventually take them all out.
That is if you weren't buried under 20ft of grenades before then
