notes to the testers/developers should NOT be written to the console.
an application should NOT write to the system log/operator console unless operator action is required.
I understand, but not sure that I agree. The application can issue the WTL macro rather than WTO. The message goes to the log, but not to the console.
Some businesses are legally required to keep operational data for long periods of time. I imagine that it is easier to issue WTL and piggyback on the archiving already done for SYSLOG rather than to invent their own mechanism** to archive and manage and easily find and retrieve the application's operational information.
** SYSLOG is an easy mechanism to save operational info. But a better choice is the System Logger (aside from the similarity in names, they are unrelated). See "MVS Programming: Authorized Assembler Services Guide", SA22-7608.