The manual mentions that in sniffer mode, the device ID is reported “of the associated endpoint” (6.4.2.3). Does that mean it cannot sniff message from other coordinators?

The manual mentions that in sniffer mode, the device ID is reported “of the associated endpoint” (6.4.2.3). Does that mean it cannot sniff message from other coordinators?

Yes, it will sniff out any packets whether it comes from a coordinator or endpoint. The sniffer is a special diagnostic mode and thus is not operating as either a coordinator or endpoint itself.