Receiving an anonymous call claiming some not-particularly-plausible threat at a particular location probably DOES deserve a police investigation. I see no reason why it impels police to drag people from their house in chains, threaten to shoot them, or actually shoot them.
If police responses were reasonable and proportionate to the plausibility of the threat then swatters would not be able to use them as a weapon.
"Swatting" isn't really a thing in Germany, but we've always had other disproportionate responses to single phone calls. One call (or even an email) that threatens to blow up the air port, or some particular air plane, and it's shut down for hours until they've looked in all the places you could hide a serious bomb (presumably, I have no idea what their "okay, I guess it was a hoax" signal is).
But what's the alternative when somebody plausibly describes a situation that indicates someone is in extreme danger? Send out a single cruiser the next day to check out what was up?
I've heard of reports of domestic violence, child molestation, things like that, and it's always the same. They rush to the place, knock on the door, look around, and arrest the people they need to arrest. What they don't do is start shooting.