Since web standards are meant to be platform agnostic they just do not get optimized down to the chip the way Apple has been doing for years. The new features released for Swift Concurrency last year will expand the divide more as developers make use of it. Efficiently using CPU cores is just not an option for the JS runtime. And HMTL does not directly benefit from GPUs so optimizations come in through CSS, SVG and other features. Most apps won't cause a noticeable difference, but many still do.