The last time I talked to Steve C. he said that one of the new improvements was an actual pressure switch for the "spray on" light. The older design just confirmend that the pump was getting power....not that it was actually pumping.
Perhaps this is for the "new" feedback from the pump. You should call SMC and see if you need a new harness.
The other improvement was to run the test button through a relay. The old button was prone to failure due to the current flow.
John