I stand corrected...There were some cases
(according to Michael Jackson) where the term "Pure Malt" was used on a single malt scotch - Cardhu for one. However, this term was confusing for the customer because for example, it was also used on vatted malts such as Johnnie Walker Green - which is in fact a blend of 15 single malt whiskies from different distilleries. So which is it? Yes, I agree a marketing technique perhaps gone bad? Thankfully the term "Pure Malt" is no longer used, however, if you see it on a bottle, it's one that has been around before the new legal term "Blended Malt" came into play. And, yes, today's bottles of Johnnie Walker Green indicate the new (legal) term "Blended Malt" on its label as Cardhu's label now reflects it's a single malt scotch whisky.
Perhaps there's more to this which I do not know, and if you do, please by all means enlighten me!