I don't think Durif was an intentional cross. Mr. Durif described his new variety as a "seedling of Peloursin". He never mentioned Syrah, so I don't think he ever knew that it was the pollen parent. I think he planted seeds from Peloursin fruit, evaluated the seedlings and chose one of them to release and name after himself. If he had made a deliberate cross between Peloursin and Syrah, he would have described it as such.

Most seedlings from a vinifera variety will be the result of self-pollination, but a few will be the result of pollination from other nearby vines. In a commercial, single-variety vineyard, nearby vines would be the same variety, but Mr. Durif was a nurseryman and would have had a lot of different varieties in his experimental vineyard (including, presumably, Syrah). So one would expect that some of his seedlings would be crosses between Peloursin and other varieties.

Carole Meredith
Lagier Meredith Vineyard