That had been my belief up until i started to write that comment, at which point i went to look it up. Having done so, i am moderately confident that the definition of "blended whisky" in the context of Scotch is that it combines malt and grain whisky. Since there are (almost) no distilleries that produce both, this also implies combining different distilleries. But it's the malt plus grain aspect which is essential.
Note that if you combine malt whisky from two producers, you get "blended malt whisky" not "blended whisky".
Ok, I partially stand corrected and partially renew my objection. The word "blended" on its own does not mean malt + grain, and leading off an explanation of scotch categorization with that definition is confusing. "Blended" is part of the name of three different categories of non-single-distillery products, only one of which is "blended scotch whisky"; the word itself simply denotes non-single-distillery products.
"Blended scotch whisky" is the term of art that denotes scotch whisky blended from single malt and single grain whiskys, according to the SWR.
Particularly when one's audience isn't experienced in this area, it would be helpful to flag terms of art, and to clarify that you're talking about specific labeling standards. The commenter had said "blended export stuff" which made it clear (to me) that they weren't speaking that technically.
Note that if you combine malt whisky from two producers, you get "blended malt whisky" not "blended whisky".