The Biden campaign has denied it ever agreed to such an inspection, and there is no evidence that Biden has ever used such a device during a debate. Tim Murtaugh, the Trump campaign's communications director, later said in a statement that Biden's team had agreed to an inspection and later backed out.
The earpiece conspiracy theory is an example of what disinformation experts call “trading up the chain,” where the sheer virality of a meme or conspiracy theory forces mainstream outlets to cover it, giving it a patina of credibility it otherwise would not have.