From the comments, you desperately want to believe in this non-human thing for whatever reasons. No one else believes that is actually true. So far, your arguments are that Grusch is telling the truth and no one is listening to him. You have ignored all the contrary evidence including the fact there is nothing documented, he has repeated what someone has said to him and that our sensors and our senses are not infallible.
The better question is why do they still believe yet another indirect claim by an alleged single “reputable” human source when every single time it turns out to be a big nothing. History is littered with examples.
If they can’t grasp the obvious pattern here and determine that it requires far, far more than some random guy claiming some agency is lying to the rest of the entire US gov then there’s probably not much to dig into with OP. The rationale is always paper thin deep borderline conspiracy stuff aka “I’m just asking questions” and any further you find a poor (or unwilling) grasp of science and a naive perspective on how the world/governments work.
Surely this time is different. All the movie stereotypes about hidden black alien programs always-US run were really true!
Why do you think non-human tech exists?