Then we don't really need ProductionOnly and PurchaseOnly for now.
Unit_FreeUnitClasses - UnitType, UnitClassType, CopyXP
UnitClassType - the unit class of the free unit
CopyXP = 0: free unit gets its trained XP if UnitType is produced, or purchased XP (usually halved) if UnitType is purchased.
CopyXP = 1: free unit always gets the same amount of XP as UnitType.
Unit_FreeUnitClasses - UnitType, UnitClassType, CopyXP
UnitClassType - the unit class of the free unit
CopyXP = 0: free unit gets its trained XP if UnitType is produced, or purchased XP (usually halved) if UnitType is purchased.
CopyXP = 1: free unit always gets the same amount of XP as UnitType.