I concur that if you experience an engine failure below 400' AGL and the ATPCS does not feather the inoperative engine, 'you' (meaning the flight crew using company procedures and good CRM practice) should feather it ASAP. This was a part of our FAA-approved training program and was worded as such in our company's immediate action items for such an occurrence.
It was not uncommon for us to have procedures that went into considerably more detail than ATR's. These were all FAA-approved.
If you want to get an idea of the impact of a failed and unfeathered engine, look up the performance penalty in terms of weight with the ATPCS/autofeather system deferred.