> In this case they're arguably scamming the government out of money, but that can hardly be compared to the crime knowingly aiding a known adversary.
I don't really get your argument. In this case they're intentionally crippling a capability of the Polish state. There does not appear to be any particular intended beneficiary (other than themselves), but any and all enemies of the Polish state foreseeably benefit when the Polish state's abilities are curtailed.
Furthermore, the general understanding of treason does not require aiding a known adversary - it requires attacking, injuring, or otherwise betraying whoever has authority over you.
> I'm disturbed by the trend of calling anything vaguely against the national interest as "treason".
I guess what I'm saying here is that this involves something that is contrary to the national interest in very specific ways. The connection is not vague.
If I'm an American and I arrange to kidnap Joe Biden and hold him for ransom, does that sound like "treason" to you? All I want is money. But someone might think there's an important difference between the effect I'm trying to produce and the effect I actually do produce.