[mbel]

Nobody would say „trujący wąż” (poisonous snake) or „jadowity grzyb” (venomous mushroom). The distinction is similar to English. There are exceptions and contexts where it can be used interchangeably but arguably the same is true for English.

[gambiting]

>>Nobody would say „trujący wąż”

No? That's how I've always said it. "Ta żmija jest trująca" - don't see any issue here. Jadowity grzyb I'll agree.

[gtech1]

This is fascinating, assuming you are both natives of Poland. Is there as much language variance in Poland as in, say, Italy ?