The OMB approval represents the approval of the Form 15. The blank form, not the contents of the filled out form.
Any form that is used by a Federal agency to collect information must be approved by OMB, and the approval typically has a three year expiration date. The 5/31/21 date is really meaningless, as the approval is routinely extended for an additional three years.
So this approval date expiration means nothing with respect to HERB.