@Alister.Frazzle Fractional distillation means refluxing not just taking cuts from three different places. The vapors do not evaporate and condense multiple times. The terpenes in your example evaporate once and then find themselves in whatever container is cold enough to condense them. That is still a single stage where you are not receiving any of the benefits of vapor-liquid interaction. Without this interaction, you cannot enrich your vapor phase.
Yes I admit that I am understating SPD a little. There is absolutely some reflux occurring and the addition of vigs or packing material helps that. However, I doubt you are seeing much more than 2 plates. All depends on how you are running it exactly. One way spinning band circumvents the issue of low reflux is allowing for “equilibration time”. This setting closes the reflux valve temporarily (~5 min) to allow vapors and liquid to interact inside and wet the column. On a more difficult separation you may have an equilibration time of an entire weekend!
Also, if you are blazing through the distillation, your separation suffers. Issues like flooding and entrainment are more likely to happen.
Something unrelated I want to point out is that higher pressures actually give you more theoretical plates. Some think deeper vacuum gives a better separation. And while there are certainly benefits to strong vac, more theoretical plates is not one.