The corded flash and auto reset flash modes are accurate. I only meter in incident mode as I am mostly a portrait photographer.
It is in the ambient mode that it is out. Both in shutter priority and apeture priority modes. I just stepped outside and took an incident reading at iso 400 @f4. The Sekonic reads 1/160. My phone's meter read 1/125 which is what my dslr read the scene at as well. It doesn't just over expose though, it can and has underexposed a scene by 3 stops before when I relied on it to meter with my C330. I pretty much just got a roll of blackness back from then.