That would be true.

However, people don't really know HOW to go about figuring that out. Or the way they WANT to do it is one food at a time, which doesn't give clear results or a faster improvement in their quality of life, if they are reacting to more than one of their most common foods... which seems to be the majority of the time.

So, IMO, the most effective way (speaking to both time and results) to isolate your best and worst foods, is to do a Total Elimination Diet... which naturally leads you into a good rotation diet... which will allow you to refine your diet more easily at a later date (identify new offenders and bring in new foods that you want to try again to see if you've healed enough to tolerate them).