The requirement is not specified in the standard but it is implied in section 4.2. If you have a copy of ANSI/ISO/ASQ Q9004-2000, look at the guidance section on page 3 and it will give you examples of the things that should be considered when addressing documentation. One of those items is relevant statutory and regulatory requirements (OSHA).
In my opinion, it is easier to manage all training in the same manner whether it be ISO, safety, process related or external. If the training is taking place as required, inclusion in your QMS should not be an issue.