Yet if both A and B know my cloud name, that may be the information to link my record in A and B. That part need to be covered somehow.
This is exactly what I'm curious about. Systems like Apple HealthKit maintain pairwise pseudonymity at the expense of having to trust Apple. Centralized credential brokers or IdPs can support pairwise pseudonymity as well but they require consolidation to a few "winners" as well and are subject to governance issues that NSTIC / IDESG may or may not solve.
Wouldn't a personal digital wallet and a personal UMA authorization server need to be introduced to A and B via a Tor-like scheme to make this work?