The EMC Isilon App & TA are compatible with both Isilon OneFS 7.X and 8.0 though there are certain API calls which are not compatible with one of the Isilon OneFS version.
Yes you are correct. Platform/3 API calls does not work with OneFS 7.X. Similarly API calls for iscsi does not work with OneFS 8.0.
The API calls .../platform/3/statistics/summary/system, .../platform/3/network/interfaces were primarily added to make this TA CIM compatible only. You should be able to use APP & TA with OneFS v220.127.116.11 without any issues.