Hey Obryn. Can you explain what that usage is. Are Encounter DMs (i) amateur DMs that don't have enough seasoning to run a session off the cuff/on the fly, (ii) DMs that are expecting to have encounter-specific props/tokens/maps and blurbs of text to advance a session, (iii) both, (iv) something else? I really don't know. I've seen that used in multiple cases and I've got an extrapolated understanding of the Encounters Program but I'm not entirely sure what Encounters DMs is meant to entail and what it does not.
4e is such an easy system to run, with such clear/explicit math and combat encounter advice that its hard for me to imagine not being able to create engaging, diverse, dynamic combat encounters off the cuff. Use large battlefield, mix in equal parts hazards, terrain powers, hindering, blocking, and difficult terrain...budget encounter...forced movement + mobility + p42 + monster math on a business card = win. Doing that off the cuff is dreadfully easy.