Honestly, I have read so much information since I started to make my juice I couldn't begin to remeber where I have read that, but I have read it multiple places. If you think about it, it makes sense. The plant they use to get a strawberry flavor from could have been sprayed with a pesticide, exposed to who knows what from the water and soil, you just don't know. Artificial flavors use the same aroma molecules found in nature. Now, synthetic, those are no good. However, I haven't come across any flavors labeled synthetic.
As far as companies go, each have their good and bad. From what I have experienced, FA and INA for the most part are the strongest. TFA and CAP are good also. Each flavor has its own specific use. A just becasue one brands strawberry works in a recipe, doesn't mean you can use a different brand and have the same results.