REST API q parameter for correctly download Work Relationships from Worker?

Summary:

We are using the q parameter to filter and download a worker's specific Work Relationship. But the response includes the correct work relationship and many more, all belonging to the same employee. How to select ONLY the one we specified in the filter?

Content (required):

Our fields parameter reads like this:

PersonNumber;workRelationships:PeriodOfServiceId,TerminationDate,LegalEntityId

and our Q parameter reads like this:

PersonNumber='12345' and workRelationships.WorkerType = 'P' and workRelationships.LegalEntityId=300000012345

The response includes the correct PersonNumber, but the workRelationships that the response includes are ALL of the worker's workRelationsips, (including the one that matches with WorkerType=P and that LegalEntityId)