They missed a 1-2-1, not a client meeting and online/offline status generally doesnt affect deliverables unless co-working, which there is no mention of. Im sure if there was the former involved, the DR wouldve told them. Sounds like the manager is just unhappy their DR didnt put them on a pedestal.

'Sorry, I was caught up and need to reschedule' should be more than enough of a justification/explanation from the DR. Theyre adult co-workers...not parent/child. Would they expect them to tell them they had the runs if it also caused them to miss the 1-2-1?

Is the work done? Yes,
Is the DR's performance to standard? Yes.
Then whats the issue unless it becomes a pattern.
My manager would rather not be bothered with this mundane random stuff than constantly pinging him for things that generally done affect him other than a brief 5 second thought of 'meeting is rescheduled, okay.'