A quick look at the preset indicates that it contains chunk elements that only contain list_entry elements and uses those chunks in the combo elements. That that works is likely accidental (instead of using a proper parser for the presets JOSM uses a reflection hack so there isn’t any consistent check of the grammar), it is definitely not documented and I would argue the preset XSL definition doesn’t allow it either.
On closer inspection it seems as if the XSL does allow a reference element in combos and multiselects. I might add that to vespucci going forward, the workaround for now would simply be to expand the relevant chunks.
PS: if you want a translated preset in Vespucci, you should extract the strings to a .pot file and use your fav translation service to translate to .po format files, see https://vespucci.io/tutorials/presets/#translation
I didn’t comment on that, but the preset references icons included in the JOSM build instead of including them in the preset zip archive. That is naturally not going to work.