I think it would help decrease your snarkiness meter reading if you also provided some specific, constructive, criticism.
What major mistakes are the author doing due to not knowing (as you seem to infer) 3D graphics well enough?
I, for one, was impressed (after grudging a bit about the talk about rectangles in the intro, which I think should be triangles to be more specific but I could be wrong, it's been a while).
Sorry about the snarkiness, I was aiming rather for "opinionated".
IMO, there are no "mistakes" in implementing how the graphics behave as they are. I'm not putting down the author, the demo is cool like I said. No, sorry, it's friggin awesome.
But! It's not an advisable production environment prototype.
First of, the content path is a bit more non-obvious than using more established methods. The extension mechanisms to the technique, as the author himself stipulated, are quite tricky.
WebGL was created specifically for rendering 3D graphics on the browser. I'm not an expert on the exact state of the art browser rendering implementations but I would expect the OpenGL context would offer a more consistent rendering on a larger set of end user devices/browsers than depending on the correctness of implementation of CSS transitions, or, on mobile devices, at least more battery friendly.
Now, if someone is looking into implementing a realtime 3D rendering solution to ones non-hobby webpage, it would make sense to research established techniques and understanding what someone is actually doing rather than jump in with this technique since to use it properly, I think you still need to grok all the stuff about linear algebra and shading models that are exposed in a structured manned e.g. in the course I linked.
I began my computer graphics hobby stumbling with vague hacky techniques years ago until I found out there was an entire well established field that teaches and extends this stuff at which point I cursed I had not found the courses and the books earlier. Just trying to save anyone's time who finds this sort of thing fascinating.
I have known a legacy codebase that would be _a_lot_better_ in every aspect had the original authors used well known graphics concepts to structure the system rather than kludges they made up along the way while re-inventing the wheel. The core concepts in 3D graphcis are not among the most complex technical things. However, there are lots of tricks and such you either need to discover on your own or read up. If you just ignore the established literature and best practices you will probably lose a lot of time hitting your head against a wall that would have been better used in drawing pretty pictures :)
What major mistakes are the author doing due to not knowing (as you seem to infer) 3D graphics well enough?
I, for one, was impressed (after grudging a bit about the talk about rectangles in the intro, which I think should be triangles to be more specific but I could be wrong, it's been a while).