Right, while the board includes such strings in the SMBIOS Structure Table's Board Data structure, the WMIC command is only capable of extracting strings that are provided in the System Data structure. Since Intel shipped only a board product, not a system product, the integrator (or the user) was responsible for filling in these strings - and Intel Integrator Toolkit (ITK) is the tool that they provided to do so.
For your board, you need an earlier version of ITK. I would get v126.96.36.1995. You should be able to get it through Intel Customer Support (contact them directly). I have also seen a place or two on the web where it can be downloaded (I found it googling "188.8.131.525"), though I cannot vouch for the integrity of these download sites.