Yeah, the Starlink launcher was a pretty specific device designed around the Starlink satellites. The attachments shown in the attached link are the ESPA (EELV (Evolved Expendable Launch Vehicle) Secondary Payload Adapter) [1] rings. They work well for a variety of customers using it because you can put out a generic document for an interface and a box you need to fit within. The first dedicated rideshare program like this was the STP-2 mission. [2]

[1] https://en.wikipedia.org/wiki/EELV_Secondary_Payload_Adapter

[2] http://www.planetary.org/multimedia/space-images/spacecraft/...