Where a list has a note to describe Dismountable troops, i.e Lydian Provincial Cavalry (1408), do the additional optional Characteristics that are paid for go with them, Dismountable rules page 128 covers missile and melee weaponry , ie if you have a bow you keep i,t a short spear you keep it etc.but not Optional Characteristics, in the Lydians case melee Expert
The note describes the unit your dismounted TUG will become in the lydian's case :
QuoteNote: Lydian cavalry dismount as Formed Loose, Protected, Short Spear of equivalent quality.
If they had "melee expert" while mounted they simply loose it. It's not in the description.
Does that answer your question ?
If the characteristics when dismounted are defined in the list that is what they dismount as (Appendix 1 U.2).
The provisions of Appendix 1 U.3 apply to troops that have nothing defined in their list - hence "Others dismount as follows" :D