WHen using a Data source in WFC Forms, there are 2 limitations that need to be dealt with. 1. Data source needs the ability to filter data based on another field 2. Data source needs to be able to handle filters in a view for sharepoint. Since a sharepoint list can technically handle 20K rows most admin create filtered views to deal with this much data. If data source can not filter in the form, then the developer needs to filter in the list.
Thank you very much for posting your feedback. The data source variables feature today, provides you the ability to create a condition to filter your data on both cases. If we did not understand the feedback correctly, please elaborate further.