[merlight]

Just guessing here... Since veteran points functions still exist, I'd say they made that change more on the presentation level, while API remained nearly the same.

-- from playerprogressbar.lua
function ZO_PlayerProgressBarCurrentFragment:RefreshBaseType()
    if(self:IsShowing()) then
        if(GetUnitVeteranRank("player") > 0) then
            PLAYER_PROGRESS_BAR:SetBaseType(PPB_VP)
        else
            PLAYER_PROGRESS_BAR:SetBaseType(PPB_XP)
        end
    else
        PLAYER_PROGRESS_BAR:ClearBaseType()
    end
end

PPB_VP uses GetUnitVeteranPoints("player"), GetUnitVeteranRank("player"), GetNumVeteranPointsInRank(rank) where
PPB_XP uses GetUnitXP("player"), GetUnitLevel("player"), GetNumExperiencePointsInLevel(rank)

edit: a bit strange that they use GetUnitVeteranRank("player") > 0 to check you're veteran, in other places they still use IsUnitVeteran("player") so that function wasn't removed, either.