You don't need 'the proof' to start in on busying yourself coming up with excuses and mental gymnastics to favor your own side.

Since there is no plausible reason for the Russians to put two small missiles into a Polish crop field, the question is whether it was an accident or some sort of a desperate hail-Mary false-flag type thing on the part of the NaZioncons.  Both are plausible.  Another remote possibility is that indeed the Russian (who made the system in the first place) hijacked the device and sent it in some random direction.

If I were to stoop so low as to make human shields out of nationals as a strategic military doctrine, I would at least try to arrange some sort of self-destruct for the AA missiles so that when the lose targeting and fall to earth at least I wouldn't have to explain 'killing my own people.'  Seems like that for the Zelenskj crowd doing so, killing Ukrainian (civilian or military) is a feature and not a bug.  Maybe do a few Polish farmers as well just for shits and giggles.