I think you are agreeing with my point: if you can synthesize pure THC you can compare its effects to the cocktail of substances that is cannabis and identify CBD as another active part of the equation. Once you synthesize both you can look for a third, and so on. You can then much more quickly study interactions and combinations. Waiting to genetically create a different combination of all these substances is going to be much slower. Also it allows you to combine them with other substances to study those interactions. Imagine a study of a combination of CBD, a beta blocker, and psilocybin. That would be a difficult thing to do if you start with just the plant material, but easier with pure substances.