Well, Apple's devices presumably don't have any trouble rendering SVG on CPU. As explained in the intro, the embedded CPUs on the blenders do. The unusual part here is that they decided to fix it instead of just falling back to a less featureful UI framework, which I'd say demonstrates an unusual commitment to quality user experience (or if you want to be cynical, flashy user experience).
Thanks for your comment : that makes more sense now.
I had the assumption that efficient SVG rendering in Safari was critical and a UX bottleneck to work on from an Apple perspective, but maybe Apple hardware makes it moot.
It's not the hardware per se. CoreGraphics on macOS/iOS utilizes the GPU for painting, which is much faster than software rendering. Cairo, used for the Linux GTK/WPE ports, is software based, and thus much slower, when painting large scenes.
Therefore for embedded devices using WebKit/Linux GTK/WPE ports we see a huge improvment with the layer based engine. Also macOS/iOS benefits though -- animations are even faster, and you don't easily run into problems, when animating parts of a complex document. It's shown in the video linked in the article at the end: > 20% frame rendering time improvement on an already quite efficient rendering pipeline (Safari / macOS using CoreGraphics on M1 machine).
