The Special Combat Forms in 11.9 on page R11 are different though.
Deliberate battle requires both forms of supply, though it doesn't say you have to expended combat supply.
Mobile Battle apparently requires neither...which is odd.
Apparently, the supply cost was left out:
This was not in your question, but the requirement to be in both general and combat supply is missing from 11.9B (see third bullet of 11.9A); probably a victim of "squishing" the rules to make everything fit. So yes, the dump does have to be expended. It does not actually have to be expended during the movement phase, I think what I did was to conflate a playtesting short-hand we used: we expended the dump when we placed the Mobile Battle marker. You may of course wait until the combat to make the expenditure.