No it's not. DC is one of the most paranoid areas around, a significant portion of the population constantly thinks someone is out to get them. Three of those people now have symptoms without a clear medical cause.
>wouldn't make sense if it were just a dog reacting to their owner's anxiety
But it would make sense that the sick, stressed owner accidentally fed the dog something bad, or accidentally kicked the dog without realizing it, or forgot to feed the dog forcing it to eat something bad.
As for Polymeropoulos, he felt sick, completely got over it, then started worrying that the illness may have been the Havana syndrome. Only then did the more serious ailments occur.