That is incorrect. Whoever wrote that (assuming it's what he actually said) doesn't know what he's talking about.
"Beer" can easily surpass 10% ABV.
Sierra Nevada Bigfoot, for instance, is 12% ABV.
And there are hundreds of "beers" in the U.S. that top 4.5% - even in Utah, the state that arguably has the most stringent ABV laws in regards to beer.
In example: pretty much anything with the word "Imperial" in it would surpass 4.5% ABV.
Speaking from personal experience as a professional brewer, I regularly brewed a commercial beer that was at 7% ABV in the States.
I brewed another production beer that was 6% ABV, and another that was 5.7% ABV.
I've also brewed a number of specialty commercial brews that have topped 10%. Barley Wines, Belgian-Style Tripels, etc...
And that's just on the commercial side of things - without touching on the homebrew community in the U.S... which shares thousands - if not hundreds of thousands - of 4.5%+ batches of brew every year
"Malt Liquor" (which I've also personally brewed and, in fact, won a 'Great American Beer Festival' medal for a batch of) is a style of beer that uses light (if any) amounts of hops, specialty yeast, and is generally infused with other sugars such as corn syrup. It's generally high in alcohol, but that's not what entirely defines the style.
