This DateAndTime value is the timestamp when this finite-state-machine workflow finished (or was last updated) for this internal backplane link. It matters on the finite-state-machine record UCS Manager runs while it discovers, acknowledges, or brings up that internal server-side backplane link because it lets an admin measure how long a discovery or bring-up operation actually took, and spot one that is taking abnormally long by comparing it to the current time. A completionTime that never updates past a link's initial provisioning on this link, even as chassisId 2 sees other changes, suggests this particular workflow never actually finished.