After the initial set up the data loading scripts started the dgraph processes. (That is what it seemed like, as they started after those scripts were run.)
But now they start when the Platform Services (aka EAC) is started.
And a second part to this question - when the dgraphs start they already have data loaded. Where did they get that data? Don't the data loading scripts need to be run for them to have any data?
(Guess I can't delete that post.)
Coworker answered my questions. Once the data is grabbed/processed from the relational db, it is kept in flat files. These are used by the dgraph process when it starts. After the very first data load the dgraphs are started by the EAC.