Correct, because the client we are using only allows mana percentages to be displayed and keeps the actual "value" hidden. Later clients do allow this feature.
On a side note, you can download older versions of a la carte pieces or if you are lucky find older versions of complete UIs from late 2003 to possibly mid 2004 range. You can even use certain pieces up to when the most recent complete UI revamp was done. Keep a back up UI folder, apply piece change, /load, if it works keep it, if it doesn't revert to back up.
If you are comfortable w/ the rather simplistic altering of xml, you can remove the mana values by just deleting the pieces within the file