The point isn't simply "class removal affects cascading", but "anything upstream is capable of placing the original content in an unrecoverable state".

Where "anything" could be your framework, your CMS, you or your coworkers a few years after the original CSS has been written and you can't fully remember what ".format-header__nav-wrapper:not(:last-child) .model-header__nav-wrapper:not(:last-child)" is doing.

And yes, that's a real CSS selector from a refactoring job I'm doing right now.