Andrew - it looks like your issue is closed now on Github. Would you like to share what worked for you?
Hey I closed that issue because my problem diverged from the original question on that github issue. I made a new issue here Register web data connector asynchronously? · Issue #141 · tableau/webdataconnector · GitHub
I still haven't been able to figure out if it's possible to do what I want, so for now I had to change my approach and generate a web data connector URL that uses the filters a user created previously in the app and the user would have to manually copy the generated URL into the Tableau Web Data Connector interface. It's not elegant, but seems like all I can do for now.