To expand upon Tim's note:

ENL = Engine Noise Level
MOP = Means of Propulsion

IGC does not allow ENL to be used for electric or Jet engines, they must use MOP sensors.

ENL may be used for gas powered engines. This is not a new change for the IGC, but I think the OLC has just implemented the change in their software.

Many FES owners have been using ENL for years, but it is my understanding that this is no longer allowed by IGC as sufficient proof the FES was not used.