See codepen https://codepen.io/gunnarbittersmann/pen/QWQMKYw When no radius given in SVG, but with CSS like `circle { r: 1 }`, the circle is not rendered. It should work with a number value as ist does with a length value like `circle { r: 1px }`. This might be the same with other properties which are new with SVG 2 (attributes only before).
<rdar://problem/94088266>