In practice, doesn't sound very problematic to me. As long as the IoT base device manufacturer is compliant, someone can just buy a board (for "product development" purposes) and then release the source publicly.
What happens if the base device manufacturer goes under and removes their website? Then the board distributor is not in compliance.
Nah, there I agree with tzs, after the manufacturer sells the product, copyright has been exhausted and the distributor has no obligations unless they make new copies of the work.