When you see run-the-business type web apps being written in non standard technology, then you can complain. When you see a neat toy being written in non standard technology, take it for what it is.
Is it a demo of proprietary technology that happens to be baked into a couple of specific web browsers and video card drivers, or is it a demo of what's possible using a (new, emerging) set of "web" standards?
Because "WebGL" certainly sounds like the name of a standard to me, and very few people expect a "web" demo to care about which brand of video card they have installed.
And since you brought it up, "HTML5 is not standardized" is a little disingenuous. Regardless of its ratification state, companies claim and market HTML5-ness precisely to signal their commitment to open standards as opposed to proprietary technology. Or maybe it's come to mean "anything that isn't Flash." In any case, the implicit promise there is that users will enjoy app functionality with minimal-to-zero worries about client-side configuration or component choice.
WebGL has a 1.0 specification, but still is not a standard as defined by the W3C/Web Hypertext Application Technology Working Group (WHATWG). Specification is one of the steps towards reaching a standard, so WebGL and HTML5 are well on their way but not there yet. Standards usually don't care what name they're referred to as (much like 4G-advertised mobile service that doesn't actually reach 100mbps/1gbps like the standard dictates).
At this point (much like with the aforementioned 4G) HTML5 means about as much as "Web 2.0" does. It's a set of competing implementations with many cross-platform features that are almost guaranteed to make it into the final standard, and a few vendor-specific implementations that are hoping to make it (if they prove their worth). Your assertion of 'Flash-like content that isn't implemented in Flash' (to paraphrase) is quite accurate in current implementations.
To sum it up, the core HTML5 that companies actually market towards is all but standard (offline storage, AJAX-like content control, Canvas, etc). The really cool things that make the front page of Hacker News and Reddit and require you to be running the beta Chrome or nightly Firefox are generally things that the vendor is hoping will make the standard. Marketing is a powerful thing, but not always accurate.
1. User visits website with late-model hardware/OS. 2. Website says "this site requires browser foo." 3. User installs browser foo and reloads website. 4. Website says "error - check system configuration."
A technology demo with highly-specific client requirements, especially on the web, especially when the demo plays the look-mom-no-plugins card, should try to enumerate the actual requirements. In this case, the requirement that after installing latest Chrome, the fool at the keyboard navigate to chrome:flags and hit the big "turn WebGL on" toggle.
I understand why these types of doc omissions happen, but it's really a pretty serious bug. Every user that hits 1-4 above is a user who is actively dissuaded from caring about the technology that the rest of the site was designed (at non-trivial expense) to promote.
On latest Chrome: There was a WebGL compatibility problem. Please check system settings.
Yay standards?