We had some discussion with Sikorsky back in 2017 following some in-flight engine shutdowns and the upshot at the time was that the FD will remain coupled in 3-cue if a throttle is moved to IDLE or if the FD sees a torque split between the two engines, but will switch to using the single-engine limits. However, the FD collective axis will decouple if a throttle is moved to STOP, and cannot be recoupled with a throttle in STOP. In OEI training mode, the FD remains coupled, because the mode does not communicate the simulated engine failure to the AFCS and the FD logic was not designed to support the 'OEI training mode'. When in a SAR mode, the FD will remain coupled
i haven't been involved for a few years now and things may have moved on...