That's a very good point.
A lifetime ago when I was in college (Klamath Falls, OR) the winters there would usually hit literally overnight. One year I went to bed when the temperature was around +45F, and woke up the next morning to -40F and 30+ mph winds. It stayed that cold for 3 weeks. Every diesel powered vehicle that wasn't kept inside or left running (mine included) had fuel the consistency of jello with clumps of paraffin in it because the refineries hadn't switched to winter blend fuel in time for even the truck stops to switch over. There were over 200 OTR heavy trucks stranded with jelled fuel in town. The stuff that got my VW diesel going again is now called
https://www.essentialube.com/fuel-improver.html PowerKleen Arctic. Back then it was just Hydrotex Essentialube. A snowplow driver told me about it that year. I haven't needed it since I moved from there, but I started using it from Halloween through April Fools every year after that. Never had any problems with gelling after that.
I'm not familiar with ClearDiesel but it's good to know it works if I need it.
Even still, if you buy something like that one should count on complete fluid and filter change just to be sure what ya have.