Then if it was only for Volks, they would have giving 10 manpower more, not 100. When they reduced the price of sturm they would have reduce it to 300 from 340. But they didn't because those 100 manpower are only there to cover SwS manpower price.
When they did that they didn't thought about OKW being able to field 4 volks squad so fast and in fact balance was really different back then.
They started to equalize more or less all factions early game some months after with Mr.Smith but they didn't really touch OKW, OKW changes on early game level are all about pzfaut and flamnade delay and cost, not about manpower available early game.
Today the game is really different and what I see is that we're taking a lot of effort to balance SOV/USF/UKF early game because of that than simply bringing back OKW early game power level in line with other and nerf the cheeses options they have that also affect Ostheer.
Its not just about initial volks, but the timing of 2nd one, 2nd volk would arrive after 2nd rifles otherwise, giving USF edge over OKW when OKW was still supposed to be aggressive early game faction.
And what do you mean about them not touching OKW? The whole patch flipped OKW upside down and strengthened volks to terminator state as they still had shreck, but were now much more combat capable even with lower vet bonuses.
OKW was never able nor intended to filed and deploy a truck instantly, so that 100mp does absolutely nothing for their tech when they need to get 40 fuel first for med truck, only reason for that 100mp to be justified as "truck bonus" would be if OKW was allowed to field a truck instantly, like it arrived pre-tech revamp, which clearly is not the case due to zero starting fuel and 15fuel truck cost.