It's not pedantic because it has a material effect on what we're lead to believe this is. This is hacker news. A hacker knows (and cares about) the difference between a "3D hologram" and Pepper's Ghost illusion, and that distinction is important in understanding what has been achieved.

This is definitely a cool hack, but it does not involve 3-dimensional projection. This is a 2D image cast on to a 2D projection plane with no stereoscopic effect. That makes the term "3D hologram" a misnomer at best, and a gross misrepresentation at worst.

Because of this mislabeling, we're all sitting around talking about the inaccuracy of the title, rather than the fun part. That's the fault of the person who titled the article, not the person pointing it out.