It really doesn't matter, I think, whether the "English" designation is valid any longer or ever was, as it's pretty much ingrained here in the States. I think the "English" designation makes sense historically, since most American blends were essentially burlies and the types of blends called "English" or "Balkan" were usually imported from the UK. Hence, it became part of the informal vocabulary of US pipe smokers to call blends based on VAs plus orientals (such as latakia) "English" blends. Whether it is/was strictly accurate wasn't really all that important, since this wasn't a formal/legal/scientific designation in the first place. The UK blenders, for their part, never called latakia/oriental blends "English" or even "Balkans" -- they were just "mixtures." Supposedly they ended up using lots of orientals as condiments because the government didn't allow much added flavoring, but I suspect that's not really accurate since a great many UK blends were, in fact, heavily flavored (1792, St. Bruno, Grousemoor, etc.). I imagine instead that the oriental leaf gradually became a staple as the British Empire spread and consolidated, allowing for a great deal of trade at low prices. The stationing of so many British troops in the Mediterranean probably had something to do with it, too, since they were exposed to the whole range of oriental/latakia blends and a perusal of catalogs from the early 20th century shows that pipe tobaccos targeted at British soldiers (esp. officers) were primarily robust oriental/latakia mixtures.
In any case, I think we worry a little too much over the rigor -- or lack thereof -- of our collective vocabulary. Pretty much everyone knows what "English" means, and it's been how we American smokers have talked for a long time.