You have to admit that the headline achieves maximum separation between "breakthrough" and "technology". I got bamboozeled too.

> If nothing goes wrong, within a few years we'll be able to confirm or reject the axion theory of dark matter.

Well, we'll be able to reject the current axion theory of dark matter. I suspect we won't be able to reject all possible ones. (But I don't know for sure.)

That's sorta speciously true of any experiment. The space of hypotheses is infinte, you can only target one. Ruling out one attractive and well-supported theory would be news on its own. A confirmation of a particle discovery would be bigger still, of course.

The axion may not be an example of the following, but there are highly specific predictions of new particles (etc) that drop out of current theory and knowledge. Antiparticles, from Dirac is one example. If they hadn't been found there would have been no motivation to look for something much like an antiparticle, since those variants wouldn't have fit into Dirac's theory.

So not speciously true of all predictions or most (before String Theory came along!)

You both may be correct. Fundamentally though the philosophy of science prefers a hypothesis that is falsifiable to one too vague to falsify.