Using IDB2, and selecting option 1 for SYSTEMS STATISTICS, option 6 for more, and option 17 for SQL Incompatibilities (IFCID 366) reveals incorrectly the R/SYSRTN screen.
In older releases of IDB2, option 17 was the SYSRTN selection. The option selections were re-ordered in r19. An older version library and its MGSYSTEM member were found and used causing the discrepancy.
To determine the cause of the panel mismatch, issue the TSO ISRDDN from the IDB2 UI.
Type M MGSYSTEM and hit <enter>. This command will reveal the the library containing the (old) version of that member being referenced. Ensure the correct r19 version library and MGSYSTEM member are found and used.