I don't doubt there is some truth in this. Certainly if an employer can choose between a college grad and a high school grad for the same job / pay they may feel they are getting a better 'deal' with the college grad.

That the population of folks with degrees has less unemployment than the set of folks who don't have degrees has been true at least since the 50's according to the Census data. (and they have nifty new APIs to access it but alas they are down at the moment). What is less well understood are the roots of this correlation.

At one time people assumed that folks with college degrees had higher IQs or higher socioeconomic status, but later studies have not born out that hypothesis. There is something different about someone who decides to finish a college degree, in the general case, than someone who either pursues no college, or starts college and drops out.

There are of course anecdotes of college drop out successes and college graduate failures, but as a population group they seem more employable overall.

So far from the data I've seen it seems there is an aspect of this question which is not yet well quantified.