I think the OP meant that Earths magnetic field and atmosphere shields any terrestrial matter far more than than a bare asteroid that has no such protections, so it seems implausible at first glance that these things would develop or survive in open space rather than here.
I don't think "organics developed in the vacuum of space" is implied. Survived? Well we have samples now confirming, if I'm understanding the basis for the discussion (the article).
But what we don’t have is any examples of them surviving re-entry.
We also have a massive amount of those same compounds already here on the planet.
Causality is… tenuous. But not impossible.
Experiments do not tell us that something IS a certain way; only the ways it is not.
It’s nearly impossible, but it is the holy grail!
This experiment was to try to falsify one theory, yes, but as you note that is a very long way from the actual goal - or the level of certainty that the article is trying to imply.
These articles are written due to funding needs, which is why the articles are the way they are - and why the scientists themselves are likely cringing too when they read these articles. At least until the checks (hopefully) arrive.