Over the years, I've seen different grinds referred to as "saber" grinds.
I know the FFBM is called a saber grind, and my understanding is that is because it has a flat, full-thickness area under the spine above a well-defined top edge of the primary grind. The skinny does not have this well-defined flat with an obvious line at the top of the primary grind. It is a gradual grind that appears convex to me, as Tony G. says. The plunge grind shows up faintly just above mid-blade-height and deepens toward the edge.
If you hold the edge of a business card perpendicular to the flat of the blade at about its mid point (top to bottom), you can see light coming through under the card toward the spine and toward the edge, and that gap appears to widen toward the spine and toward the edge, indicating a convex grind.
Actually, my previous encounters with the term "saber" grind have been with ABS Mastersmiths who have described a convex primary grind that way, which is very close to the grind on the skinny. The strength of that slightly convex primary grind, according to what I've been told, is the basis of its use in slashing-type swords like sabers. The first time I heard the use of the term "saber" to describe a blade with a full-thickness flat beneath the spine was in regard to the FFBM. But I'm not a sword person, and my knowledge in that area is very limited.
Anyway, yeah--the skinny appears slightly convex pretty much from spine to edge. AND it's a very sweet handling knife--super deal for the money BCS is selling them for, no doubt about that.