It is, it is! SVG is DOM, with event handling on every node, with attempts to apply CSS rules. Canvas for non-interactive charts is just "draw once and forget". It is a sequence of moveTo + lineTo, then you have a bitmap and nothing else. Extremely basic graphics, modern JS engines will handle it in the blink of an eye.

I don't even mention the fact that article suggests to return each SVG sparkline in a separate request.