I seem to be having the same type of issue when using the Anchor Text API as well. Doing the call below returns only 3 results for www.moz.com.
I am pretty sure I have the right kind of account that the number of results that come back should not be limited. I have tried changing out the Scope, Sort, Filter, and Cols but every time there is only 3 results.
Any help would be awesome. Thanks.