Canuck guy,
Maybe is it a preccautionary procedure; if the chip is caused by ,let's say, a free turbine bearing things will deteriorate very quickly with a possible fire or free turbine explosion and for sure engine shut-down.
Engine on idle is certainly a better configuration to assess the situation and follow up with the procedure.
I haven't seen this amendment on arriel 2S1, do they still stipulate to make sure OEI flight is possible or is it an immediate action ?