You clearly stated that some of the surviving Death Eaters managed to flee. What is the point in obliviating the Ministry employees? The stated reason is bogus, since Voldemort can hear of the Jedi from the surviving bad guys.
The only reason I can see for doing that is to keep it out of the press.
Author's response
Hello, slickrcbd.
Yes. The ministry obliviation is to protect the employees from being tortured for information they no longer had. They can't spill what they don't know.
The escaped Deez have returned in failure. Voldemort is not well-accepting of failure. They knew he wouldn't give them much chance to explain about the clearly magical swords they saw, before he threw a tantrum. Voldemort already knows Harry has one, as that was reported to him after the Wizengamot session in July.
As for the press, Rita and Euwings both know about the lightsabers, but since nobody has ever explained what they were, or how they worked, they're still 'magical blades'.
Trust me. There is method to my madness.
Somewhere.
Alorkin