I believe as a former glider pilot that the ICAO differentiate between self launching gliders (those that can take off using the engine) and self sustaining gliders (those that the engine is not powerful enough for a take off, but will keep them airborne once they are up there). This may be the case for this type.
No, I don't think that's the case.
For example ICAO allocate codes for the Schempp-Hirth Discus, Ventus, Nimbus, etc, and use the same codes (DISC, VENT, NIMB) for both the self-launching and sustainer-engined versions in each case.
I'll talk to my ICAO contact and find out the story on the ASW-27E.