I am not willing to say these fish were snagged. I watched both videos again, and there is nothing to say that they did not bite. My original comment was more a question than a statement of fact. Congrats to the angler for a couple nice fish
With that said, those fish did not have any fight in them and were not very active if at all. I do not doubt that in certain conditions, flathead will feed in the winter the same as a “hibernating” bear will leave the den and feed during unseasonable weather conditions. It does not happen often, but it does happen and if you are there at the right time you could be the lucky guy.
I would assume that the time frame of this video was either very early of late in the year and water temps were slightly higher than a “dead of winter” timeframe. Dtro may know more if he knows the location, but I would not be surprised if this was below some type of warm water discharge.
All pure speculation