In general whether the extract query is filtered on pzInskey or pxObjclass will depend on whether the class is a classgroup or not. The pzInskey like will be when the extract is based on a class group. The pxObjclass is for when a class is not a class group. I am not sure what version of BIX you are running but in later versions the "pzInskey like" may be gone entirely and instead is a series of "pxObjclass =" for each member of the classgroup. In later versions you can remove these standard filters and instead just add whatever filter you want so you would be able to specify a "pzInskey like" if you wanted but in general the like is going to make the query perform poorly compared to the = operation.