I'm pretty sure that this is related to the old "Troubleshooting" button in R77.30 that would essentially put all IPS signatures in Detect Mode, but without actually modifying their settings (Prevent/Detect/Inactive) in the SmartDashboard:
This button did not make it into the R80+ SmartConsole, at least that I can find, and I don't know of a way to enable Global Detect for IPS. The ips off command would be a reasonable alternative to this functionality.
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