The demo is doing a setBindGroup per triangle, so not exactly surprising since this is a well known bottleneck (Chrome's implementation is better optimized but even there setBindGroup is a surprisingly slow call). But since both implementations run on top of Metal there's no reason why Safari couldn't get at least to the same performance as Chrome.
Safari has WebGPU support today, albeit behind a feature flag until it's fully baked. https://imgur.com/a/b3spVWd
Not sure if this is good, but animometer shows an Avg Frame time of ~25.5 ms on a Mac Studio M1 Max with Safari 18.2 (20620.1.16.11.6). https://webgpu.github.io/webgpu-samples/sample/animometer/