Before someone gets their panties in a bunch, I am not suggesting that STEM grads have a lack of critical thinking.
Yeah, I think part of the mistake here is in using the term "critical thinking". It's vague. And the talk about "Liberal Arts degrees" is also a bit misplaced.
I would sooner accept your description of "expansive thinking", in that it gets closer to what I think all this talk is about.
I think what's really being said is, if someone is educated exclusively (or dominantly) in a STEM field, without other things to add to their background, there will be a inclination for that person to deal with things in factual terms. In a sense, they're being trained to think about things statistically and factually, to think that things are either true or false, to be dismissive of opinions or emotions or interpersonal relationships as valid reasons for doing things. There are realms of human life that they are not only not-trained in, but they are trained to see as "without value".
The problem is, businesses-- and other groups of people trying to accomplish things-- make heavy use of those things which are "without value". When you're trying to figure out a solution to a complex problem, it often helps to have someone in the room who educated in those things "without value". Really, you want people with a bit of a balanced background, having studied various topics, including "worthless" things like literature and philosophy.
So I think what they're really saying is, there's a need of people with broad and expansive minds, able to think intelligently about many different subjects, both technical and non-technical. Unfortunately, a lot of extremely technical minds will think that's an insane statement, since only technical knowledge is needed. Really, those people are just serving as examples of the problem.
None of this necessarily needs to be bound up with degrees. I've known people with Liberal Arts degrees who know quite a bit of math and science, and people with STEM degrees who've studied a fair amount of the humanities. And degrees often fail to be an adequate measurement of qualifications anyway.