FWIW, the black hole hologram thing is best understood in the context of an idea that has been around for quite a while: the "Anti de Sitter / Conformal Field Theory correspondence". Basically, the world we think we live in feels like a CFT-world with 3+1 dimensions: local particles producing local forces as they travel through local space. But the correspondence shows that some CFT-worlds are each mathematically paired with one equivalent AdS-world. The corresponding AdS-world for us would be a 2+1 surface (something that looks a lot like a black hole) with a specific set of rules describing the interactions of the ripples on the surface. In some sense, one could imagine the CFT-world as a holographic projection from the flat AdS-world "film".

IIRC, AdS/CFT actually turned out to have a practical application a year or two back... something to do with superconductor physics I believe. So, in a sense, it's as "real" as anything mathematical is real. Whether or not it's relevant to our interpretation of reality is an open question.

Oh, except for two other tidbits that came from a completely different direction in physics.

First, The entropy of a black hole is predicted to scale with the surface area of the event horizon. General Relativity predicts that, once a black hole has formed, the volume of the event horizon grows with the square root of the mass that falls into it (because gravity falls off with 1/r^2), instead of the usual cube root of mass expected for physical object volumes.

Second, physicists have good reasons to believe that black holes are maximum entropy objects -- at minimum that's true in the thermodynamic sense of "entropy", because energy that falls into black holes cannot be used to perform work. (But information entropy is almost certainly equivalent to thermodynamic entropy anyway, so you can safely extend that conclusion to maximum information entropy if you like.)

(Side note: technically you can extract work from a black hole... if it's spinning. The "ergosphere" of a spinning black hole extends past the event horizon. As you extract work from the ergosphere, you siphon angular momentum from the black hole and shrink the ergosphere.)

Now, combine these two tidbits about black holes, and one concludes that the maximum entropy for a region of space should grow with the surface area of the region, rather than the volume. Doubling the radius multiplies the maximum entropy by 4, rather than the intuitive 8. There might be a flaw somewhere in this reasoning -- it's mooshing together relativistic physics and classical physics in a way that's not implicitly correct. But it presents a striking parallel with the AdS/CFT thing, which lends it some credence, and a lot of very smart people have gone looking for flaws in the idea and come up empty-handed.

If you combine all this together, you reach the possibility that the universe might be (in some sense) a CFT space mathematically equivalent to AdS ripples in the event horizon of a stupendously large black hole. This paper pushes that idea further, and the short summary is that the paper attempts to derive gravity within our CFT universe almost purely as a consequence of the Second Law of Thermodynamics operating on the AdS black hole ripples. However, the author might have just found a nice little piece of circular reasoning where he injected an unwarranted assumption, so it's not a done deal.