An update for folks here on this UDN issue: https://udn.unrealengine.com/questions/462412/skylight-intensity-should-not-use-cdm2.html
Epic will change Skylights to show as IntensityScale and not show cd/m2, but the change will go in to 4.22. This is good news, as cd/m2 is misleading on skylights and would add to confusion.