On my Mac the blown out white areas look absolutely gray compared to setting everything in https://threejs.org/examples/webgpu_hdr.html to max. From testing on Windows in another comment, I have a feeling the canvas on this site is only set to wide gamut, not also wide range, so you're just comparing colorful SDR to normal SDR with it.
The HDR content is literally is brighter than white on my monitors.
I wonder what is different about your setup?