Hi Michael Sampson
Sorry for the late response. We are working on adding GDPR and you should be able to find it in the next 1-2 months. Will update here when it's published.
To answer your second question, each control are composed of several actions. Organizations need to complete all the actions in the control to get the update at the "customer-managed control" bar. However, once you complete an action, you get the "action score" for that assessment right away.
There are some common actions between assessments. E.g. when you complete an action like turning on MFA in ISO 27001, you might satisfy one of the actions in other controls in other assessments like NIST 800-53 and NIST CSF. Therefore, you would see some assessments with 0 control completed, but they have some common actions completed when you assessed other standards. The score of those actions will be reflected in the assessments.
Let me know if it helps.
Thanks,
Tina