Hi Steven,
Completely agree. My inital post asked for additional information to be posted with this maintenance notice.
for example a much more informative (and helpful) message would be:
"AGOL is undergoing maintenance on March 19th, 2019 between the times of 5pm and midnight PST.
The nodes that might experience distruption to service are:
"services5.arcgis.com"
"service2.arcgis.com"
"datahub.esriuk.com"
*list of updates carried out*."
In Steven's case - this might have allowed Steven to distribute a message about the distruption to service across his company/organisation.
If Steven's layer was of significant importance to the organisations function, this would have resulted in a significant loss of service.
I'm not sure why Kelly has marked her answer as correct.