In the US it is usually considered unemployment of under 4% because there is always about 4% of the economy who are eiter unemployable (the deranged, the druggies etc) or in the process of changing jobs.
In the US it is usually considered unemployment of under 4%...
What you're describing is what economists call Full Employment.
A labor market can be tight, with a shortage of qualified workers, or it can have a lot of slack, with plenty of available labor, but I don't know what "full" would mean.
Either way, the article's premise was that unfilled job openings defied the notion of a full labor market.
I think it's just a case of incoherent business writing.
BTW, please pardon my pedantry.