MT4 delivers no volume, and cannot deliver it since it's mainly a Forex and CFD trading program. Forex and CFD have no volume. You confuse that with the tick frequency.

You can see that it's really the tick frequency when you display marketVol() on EUR/USD live with an MT4 connection, and at the same time observe the ticks in the MT4 terminal. That's why the manual mentions "tick frequency" for MT4 marketVol, not "Volume". And no, there's no historical spread by MT4 either, at least as to my knowledge.