I visited the salon in Geneva in March of this year to collect my new watch, ref 5565,
I also handled a number of minute repeater wristwatches including the 5078, which does not have Cathedral
Gong, but still does have a fantastic sound.
The reason for this is that the case diameter isnt large enough(at 38mm) to accomodate the additional length of chime
bar to give the Cathedral tone
The ref 5079 and 5074 do have the Cathedral gong as their case dia is approx 42.00 mm
I hope this is helpful,
Tom