CA Spectrum NCM's Global Sync Task (GST) adds all devices from NCM Device Family membership into the Remaining Device List for the GST even if devices are in Maintenance status.
CA Spectrum lets you disable active device monitoring using Maintenance mode status for the devices. Maintenance mode applies to Network Configuration Manager (NCM) functions as well, so when Maintenance mode is enabled NCM functions will not work.
This is working as designed.
The underlying intention, ahead of the active monitoring for the device network status, is to provide a full list of all recognized devices from the NCM point of view, which that option can work on. As a result of this list, the administrative user will find in the Global Sync Task output that the devices set to Maintenance are listed under failed devices, indicating that these devices are truly not processed and captured by the CA Spectrum NCM GST.
The CA Spectrum NCM GST implementation will not contact the devices in Maintenance status using any configured protocol (that is, SNMP, telnet, sftp or ssh/scp). This matches the overall understanding for the Maintenance status in CA Spectrum.