I think its a general reference to losing the popular vote but winning the electoral college and otherwise having nothing to do with the electoral college margins.
There is some analysis that boils down to the below:
“He concluded, with help from The Cook Political Report, that the election hinged not on Clinton's large 2.8 million overall vote margin over Trump, but rather on about 78,000 votes from only three counties in Wisconsin, Pennsylvania, and Michigan (by the same logic, Obama won in 2012 due to three counties in Florida, Ohio, and Pennsylvania)
That's one way of looking at it. Another way, is to break out how many of those electoral college points were won at razor thin margins. The reality is that the election was VERY close. 107,000 votes in three states decided the whole darn thing. WI, MI, PA, and FL were won by Trump with less than 2% margins each.
304 to 227 wasn’t a “squeak”