Fractionation is a chemistry/engineering/industry term that is used to describe the separation of components from a mixture. Commonly based on their relative vapor pressures, but other techniques such as chromatographic or such also are encompassed. It does not mean separation of a pure component, just separation and enrichment of a phase with respect to at least one component.
As such, fractionation is occuring. This is mostly used in industry to describe distillation systems with multiple stages to purify products from mixtures.
I have never heard the myth that all of one species could vaporize, but it wouldnt surprise me to hear that be spewed around by the same folks that think the cannister pressure has something to do with how full it is. Most persons cannot be expected to have had the courses necessary to understand what is occurring.
Seems that a common term, is actually being mis-applied to that myth, but I would say that fractionation is occuring.