It's those commentators who are confused, say the Merriam-Webster editors.
"Times has now been used in such constructions for about 300 years, and there is no evidence to suggest that it has ever been misunderstood."
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They also dismiss the related idea, often invoked in newsrooms, that "five times more" isn't synonymous with "five times as much," but really means "six times as much": "It is, in fact, possible to misunderstand
times more in this way, but it takes a good deal of effort."
I've heard people argue that
threefold and its brothers are ambiguous, too, but I doubt it. The Oxford English Dictionary says
threefold has meant "three times as much" since it was an Old English word; it seems perverse to keep looking for ways to make it mysterious.