LLLK:
I think that automated holding is a very grey area - there is no recognised industry standard for FMS/FMC to fly conventional holding/racetrack or RNAV holding (other than PANS-OPS) and different manufacturers have made different design decisions.
The ARINC boys developed holding standards for FMS platforms a long time ago. Alas, these non-pilots failed to really understand the FAA or ICAO specifications for holding.