Would it really affect battery consumption in any meaningful way ?
probably though not massively if it's the odd site; very likely if it'a all sites. Not massively if it's the odd element in a page, very likely if it's all elements in the page.
But perhaps more importantly the smoothness of the UI on scroll might be negatively impacted - and there is a lot of up and down scrolling in the mobile world, isn't there?
in other words, not everyone has an iphone 13 or other android-based extremely high-end mobile device at their disposal.
but yes it looks nice :-)