Found it!
In the sound setup menu [FUNC + TRIG] the octave setting of the preset kick is -3.
When I change this to 0 the preset kick now sounds indentical to my identically programmed kick.
Apparently you can set every sound’s base octave individually in this menu.
For kicks it makes sense to lower this a few octaves.
Was difficult to find that out though, happy to have returned from the bottom of the rabbit hole.
The manual says:
9.4.7 OCTAVE
Sets the base octave of the Sound. This setting makes it easier to play the sound at the “right” octave on
the Digitone keyboard. It also makes sound locking more practical since you can control the octave setting
on the sound and minimize the need to transpose the sequencer notes to make two or more sounds
work together.
Many thanks for taking the time PTSowns