Waxing even more pedantic, there are two things wrong with this statement:
1) Common VG Nic base is 90% VG (with a small amount of water impurity) and 10% nicotine. Pure nicotine has a a freezing point of −79°C (−110°F). So that 10% likely has a huge effect on the freezing point of the mixture, even more than the fraction of a percent of water that’s also present.
2) Just because something freezes (turns solid) does not mean it expands in volume at that point. Water is rather unique in that property. Vere few other substances do that; most anything other than water will continue to shrink with decreasing temperatures, and if you have something that continues to shrink, it won’t crack its container by shrinking.
In the end, from a purely pragmatic perspective, you are correct. There is no worry about nic base (either PG, VG) freezing solid (it won’t at home freezer temperatures), or expanding at in volume at lower temperatures even if you could get it cold enough to turn into a solid.