Depends if we consider holograms only the specific technique of using phases to encode the information or any general technique that can encode 3D information on a 2D surface.
This solution relies on a physicals height map (in the author's word, a 2.5D surface), whether that counts as a 2D surface I don't know.
(and yes, I also saw the great explanation from 3blue1brown).
It isn't projecting a 3D surface (I'm not sure that even makes sense in this context) and it isn't storing volumetric information.
It is just using refraction to make brighter and darker areas in its shadow/caustics to make an image. The paper is 10 years old at this point and linked by this article.
I think once you read the papers you will realize that the only thing 3D is the surface of the lens and that is only so it can get curves and angles for the refraction.
This solution relies on a physicals height map (in the author's word, a 2.5D surface), whether that counts as a 2D surface I don't know.
(and yes, I also saw the great explanation from 3blue1brown).