I’m not sure about DNx specifically, but Avid has certainly received quite a few engineering Emmys over the years.
Remember that ProRes is a family of acquisition, post, and delivery codecs, which now includes a camera RAW codec. I believe that’s unique, although I suppose you could stretch the RAW definition a bit to include Cineform or DNx RGB uncompressed.
In any case, an award like this is in part due to the impact on the industry. I would dare say that ProRes has had more overall impact on the business for a codec, than has DNx, in spite of its SMPTE certification.
If you review the rest of that video, quite a lot of other ideas and products received Emmys, too, such as Teradici.