"Administration of additional write / change permissions" permission is disabled in service plan for Reseller, but Reseller can see and tick this permission in his own service plan.
Why it's possible ?
Despite of the fact that Reseller can tick "Administration of additional write / change permissions" in his service plan service plan will be created without this permission following warning appears:
Warning: Unable to grant the following permissions because they conflict with the reseller plan: Additional write/modify permissions management.
Subscription created under Reseller will not be sync with service plan and additional permissions will not be applied.