I thought the term English Walnut refered to wood that comes from English Walnut trees (typicaly in California) that were past their prime and cut down for their lumber. I also vaguely recall reading something along the lines that English Walnut cuttings are often grafted onto Black Walnut saplings as a means to increase English Walnut production (the nuts, that is), again mainly in California. I've heard said wood denigrated for being too soft. Not so in my experience. Maybe I've been lucky.
Whatever the source, I personaly like the looks of the lighter colored "English Walnut". (I like cracking English Walnuts at Christmas-time too!)
