Yes, and for a very mundane reason. When an application is long-lived there’s inevitably some bit rot where one layer (template, style, or JavaScript) gets removed for some reason, and one or more of the corresponding layers is accidentally left in the code. This is especially likely to be CSS.
With single file components it’s much easier to track the dependencies and rebuild / scrap chunks of code without leaving cruft around accidentally.
In over 10 years I've never worked somewhere where anyone was trying to prune unused CSS, especially in the traditional approach where you just have large .css files that become append-only.
Not until I experienced component-level CSS did I see it happen since now it's relatively trivial to see unused CSS.
i would buy this argument, because i have seen this happen with WPF/XAML (person deletes the markup and code-behind, but accidentally leaves the viewmodel), except that in the webcomponents world i would imagine you'd have all three files living alone in a folder named after the component.
With single file components it’s much easier to track the dependencies and rebuild / scrap chunks of code without leaving cruft around accidentally.