The real story here is the apparent... and I use this term very, very deliberately... fecklessness of all the relevant authorities. Apparently... again, a deliberate choice... nobody has the authority to figure out what is going on, or nobody has the motivation, or nobody has the technical capability, or
something like that. I'm not sure what the problem is, exactly, and that is in some sense now the dominant problem. How can there be no clue by now?
Your sort of post is relevant in the first few days of the story. But if this was the case, with all this attention on it, it should already have been determined. But authorities aren't even floating this as a theory. Basically all they're doing is shooting down (pun somewhat intended) every theory.
That there is this much confusion, days later, is itself now the most important aspect of the story.
And we're getting up to where there are international consequences to this sort of issue, too. If we can't figure out what these drones are in a week, how can we be trusted to defend Taiwan or other allies in a world where "drone swarm" is slowly but quite steadily moving its way up to the #1 most likely attack vector? At some point it stops mattering if maybe it is just helicopters miles away being misidentified, at some point that becomes even worse in some ways than other answers, as it gets hard to claim we're going to be totally awesome at defending you against drone swarms if we can't even figure out in less than two weeks whether or not there are drones in our own airspace.
I don't know what's going on and am not pushing any particular theory. I've got a lot of things in my probability matrix but none of them particularly make any sense at all, which means I'm missing something critical. (Which is hardly a surprise.)