They also point to the differences between the representation authorized for the unrestricted categories and H-2A  for the former, grantees may represent eligible aliens on all matters; for the latter, representation is restricted to matters arising under the employment contract.
The unrestricted categories have to be represented in some manner. 
mnli hypothesis: The unrestricted categories have to be represented in some manner.  premise: They also point to the differences between the representation authorized for the unrestricted categories and H-2A  for the former, grantees may represent eligible aliens on all matters; for the latter, representation is restricted to matters arising under the employment contract.