I wouldn't consider other chromium browsers reskinned because they're using the chromium engine as a dependency, by choice. They can customize it as much or as little as they want (and I'd imagine they do to various extents).

Browsers on iOS can't - they are required (legally, not technologically) to use (a worse version of) Safari's engine. Chrome for iOS is not the browser that the chrome team wants to distribute, it's a browser Apple made that has been customized to the extent that Apple allows it to be customized. What is that if not reskinned?