UPDATE 21/4/22: Nintendo has now responded to the filing of an official complaint which alleged company interference in an employees efforts to unionise. The company has said the claim was made by a former employee who was fired by Nintendo - but that the person in question was terminated for disclosing "confidential information and for no other reason".
Here's Nintendo's statement in full:
"We are aware of the claim, which was filed with the National Labor Relations Board by a contractor who was previously terminated for the disclosure of confidential information and for no other reason," a Nintendo UK spokesperson told Eurogamer today. "Nintendo is not aware of any attempts to unionise or related activity and intends to cooperate with the investigation conducted by the NLRB.