Mingrelian ethnographer Tedo Sakhok'ia wrote in 1903 (in a series of newspaper-articles, republished as the final chapter 'Abkhazia' in his Journeys in 1985, in Georgian) of Mingrelians flooding into Abkhazia in the wake of the Russo-Turkish war of 1877-8, where they revived commercial activity, but the truly massive importation of Mingre- lians took place, as stated earlier, in the years of 1937-54
It is true that Mingrelians moved into Abkhazia, yet this does not mean that the two groups of people lived separately. I am Mingrelian and my older family members have told me about how they had to leave their Abkhazian husbands and wives. The two groups interacted with one another and sadly as a result of the Abkhazia War those integrated families had to be split up.
It is also good that the author made use of a primary source to verify his words. Previously he had mainly been pointing out the various mistakes in Donald Rayfield's book, which I have not read, but I doubt was published containing the incorrect historical facts. I just believe that Hewitt's opinion is in opposition of Rayfield's, so he found means of disproving them.