We have some organic ‘building block’ compounds confirmed frozen on some asteroids.

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.

Causality was not the point. The point was to refute the seeding hypothesis, and because they found those molecules, the effort to falsify the hypothesis failed. Now we can move on to the next attempt to refute, which, as you say, might be to study whether molecules can survive conditions of reentry.

Experiments do not tell us that something IS a certain way; only the ways it is not.