Yes, unride-able. They changed the bike course at the last minute. There was too much snow that would not pack down. Very few people can ride consistently in more than an inch or two of snow, and even then it is intense work to stay upright. The bike course ended up being almost 90% pavement. It was 3 loops around Phalen with a two short off road sections, and one longer section.
I've watched Tom Puzak and other fast people at the Wednesday night fat bike races, and even they end up running through deep snow until there is a track cut by the bikes that evening.