I think there are several issues here:
First is that in this scenario you did intend to move marine life (live rock), you just weren’t sure what exact species were there. The goal was to seed the aquarium with a variety of lifeforms, and you are intentionally creating conditions that support those organisms. This is sort of akin to planting a seed intentionally, but not knowing what plant species the seed is of, or tossing a seed mix into a lawn or meadow without knowing the exact species. Those plants would still be cultivated, even if you didn’t know the exact species (or accidentally planted the wrong things!).
I agree that the initial organisms colonizing the rock could be considered wild - however, they’ve now (mostly at least) changed a life stage, which is a general cut-off for considering something to move into captivity (see discussion on bringing caterpillars/pupae into captivity to protect for transformation as @annkatrinrose mentioned). So making observations of a different life stage would be an issue.
If there was an organism that you definitely did not intend to come into the tank/didn’t expect to be on the live rock, I think that you could make a case for an unintentional introduction and that it might be wild (like a disease/parasite?), but that wasn’t in the original question.