That was the schema documentation for the control access right for group
membership in that last link. The schemaIDGUID is used when setting a
property read or write ACE for a specific attribute. The rightsGUID is used
when using the control access right.
In this case, you can either use the member attribute directly or use the
control access right (which just points to the member attribute).
The schemaIDGUID for the member attribute is in the same general part of the
schema documentation that the last link came from.