The first thing is that they do meet the specifications for rise time, voltage stability, short circuit protection, etc. that the ODVA recommends for DeviceNet network power supplies.
The second thing is that they've been run through the ODVA tests for power supplies, to prove that they actually do the things the specifications say they do.
DeviceNet doesn't require anything *special* for the power supplies, like ASi does. But it recommends certain performance characteristics, and buying a power supply that's been tested and conformance-marked is an easy way to be sure it's going to work in that application.