Wheat that is not meant for brewing is treated with a desiccant so they can harvest a little earlier, and have a slight increase in yield. Desiccant is not the proper term, but it's what farmers call it. It is really just Roundup, a Glyphosate, which is linked to health concerns and is banned in parts of Europe. Also, there are different varieties of wheat that may be more suitable for brewing. Maybe I'm picky, but I consider "feed grade" grains to be inferior, and won't use them for brewing. Brewing grains are chosen for qualities that make them more suitable for brewing, and their specifications are recorded and listed by the maltster or grain supplier.
As you mentioned above, unmalted wheat is good for use in Belgian style Witbier, but raw, unmalted grains must have their starches gelatinized before adding to the mash.
Sorry to ramble on with my opinionated comments. Good luck with the wheat and your brew.