you are correct - however I thought you were only speaking of devices that had a driver of some sort - in which case Implements DCE will always be checked.
Some device templates only require an external package for example, in which case Implements DCE will not be checked, but it will have a package listed. This is how LMCE knows what dependancies to install.
In short, Implements DCE will tell LMCE that there is some sort of driver (executable, GSD whatever) that either sends commands, datat or responds to events.
Probably should distinguish what is meant by driver here - the driver for a device that interacts with the DCE "network" ie receives/sends DCE commands and events between itself and the router/other-DCE-devices, and translates them into actions for the "thing" it is controlling. As opposed to common or garden "drivers", for instance a driver that controls a remote like the Fiire - this has a device "driver" that needs to be installed, but doesn't interact with the DCE system at all. It is just a normal system driver that interacts with the kernel. In this instance the device template is just used to allow pnp identification and installation of the required driver, no actual DCE interaction is implied...