My team mainly using SQL server as data source. We have many relational tables and look-up fields. It is taking time for us to implement responsive comboboxes sometimes. When i saw this function i got exiced. But also when i see this statement in the article "At this time, you can use lookup columns only with SharePoint and Common Data Service for Apps." i felt sad. It would be nice to support such a functionality in SQL data sources as well. I am not sure if this idea is already posted or if there is a planned work on this or not but i am sharing it.