It is none of the above. It’s an expression that people use to subjectively express how something makes them feel. In this case, there are certain characteristics to this typeface that lead people to say they feel “warmth”.
Just like when you go to a really happening party and say, “it feels alive in here”. Would it hold up to a randomised trial? Probably, or probably not. It doesn’t matter. The point is about how it made someone feel, and we now know. How would it make you feel? Whatever the answer is, is your perspective and your truth.
There’s a time and place for predictable, measurable results from randomised trials. This is not one of them. None of the great art from history were the result of scientific rigour.
It behooves one to observe reality through multiple perspectives, and question what the meaning of “real” is. I sense that randomised trials would not yield measurable and predictable results for this either.
In this case, "warmth" refers mostly to the rounded corners and unique design quirks, which are meant to imply "I was crafted in analog by a seasoned master draftsman, not merely constructed from sterile geometric shapes by some hipster on a Macbook."
I have never made a font, but I have a implemented many text rendering systems over the years and worked with thousands of fonts.
I do find some warmth in their typeface.
The typeface looks sloppy and unrefined on my 4k windows machine running chrome. Certainly not functional, utilitarian, or elegant. The stems are of inconsistent width and glyphs are generally of inconsistent weight. I'm picking up no 'manufactured' vibes from such an organic look.