You are using Canvas right now. WebGL uses Canvas to render to the screen. If you open up your demo's DOM inspector right now, you will see a canvas element. It's:
<canvas id="the_canvas_id" width="1914" height="580" style="width: 1914px; height: 580px;"></canvas>
It's a little bit hard for me to trust this kind of dismissive talk about the browser adding too many abstraction layers when it's not clear to me that you're fully aware of what browser features your demo is using right now. Targetting the DOM and using embedded canvases really doesn't have anything to do with whether or not you're writing Javascript, and it doesn't mean you can't use WebGL to render charts.Ehhh sort of. Canvas is much older than webgl. When we talked about canvas a few years ago, that always referred to the canvas DOM element and its associated 2D shape based API. (fillRect / moveTo / lineTo / etc). When Webgl appeared, the nomenclature was "using canvas" vs "using webgl", since webgl's API is completely different from the 2d canvas API.
But browser manufacturers didn't give webgl its own DOM element. Webgl also uses a canvas DOM element, then configures it differently. (getContext("webgl") instead of getContext("2d")). So if you're using webgl (which I think this app is doing), then you're "using canvas" in the sense that your HTML contains a <canvas> element. But you aren't using the canvas 2d API - which, as I said, is totally different from webgl and is also called "canvas" because it was here first. And it doesn't have another name.
In defence of the GP comment, I think its pretty clear from context that "Canvas layers on top of WebGL/GPU draw calls" refers to the canvas API, not the canvas DOM element.
If it's just a context misunderstanding of what specifically "Canvas" is referring to, fine, I don't mind clarifying what I mean by that. And you're right, it's not unreasonable for someone to see the word Canvas and think "2D APIs." But I just want to be very clear that targeting the DOM for UI controls doesn't mean you can't use WebGL or WebGPU and direct graphics programming for charts, or that you can't render a chart in a web worker and then use the pixel buffer with a canvas. And none of that stuff requires you to program in Javascript (except for glue code, which you'd have to write for all of those methods no matter what). In modern web terms when I talk about targeting the Canvas, I just mean rendering pixels onto a canvas element as opposed to manipulating the DOM, regardless of how or where those pixels are calculated.
There is no additional set of abstractions you need to go through to do that, and there's no graphical system for the web that gets rid of the singular abstraction of needing to eventually put the pixels onto a canvas element.
Yes, if you were calling browser 2D APIs, that would have an additional performance cost, definitely. In a context where that's not performant enough, then don't do that? But there seems to be a suggestion in this comment thread that embedding canvases would require working with a higher level more abstracted graphical API when rendering the charts, and that's just not true.
I didn't test Canvas specifically in my explorations, but I did test a few JavaScript based frameworks, and the ones I found that were efficient sat on top of WebGL, not Canvas. Ultimately I didn't pick those because they had a bunch of other stuff baked in that I didn't need or want, and were already equally non-native (sitting on top of WebGL). And I frankly didn't want to be writing JavaScript.