Yeah I suspect grafting although in most years produces perfectly good fruit isn't quite a good under extreme pressure such as this drought as for example a fruit from seed.
There is a pear tree here from seed that had some potential phytophora issues and half the bark died and I nearly chopped it down but despite the bark it's looking pretty good compared to the rest of the pear trees here. Apart from that tiny comparison I have noticed all the wild hedge row fruit doing far better than grafted and even long established transplanted plants this year. Wild blackberries are doing well compared to the cultivated ones I have.