Why does the general-sibling combinator allow toggling pseudo-element's content, but not the adjacent-sibling?

Question

In this question \"CSS3 Selector That Works like jQuery's .click()?\" I posted an answer using the :checked state of an input, of type=\"

Answer 1

This is a long-standing bug in WebKit browsers related to the use of certain dynamic pseudo-classes with next-sibling combinators. This happens whether you're applying styles to the sibling element itself or a pseudo-element of that sibling element.

I don't know if anybody has filed a bug report yet, but this has been seen rather frequently on the site:

• Webkit bug with `:hover` and multiple adjacent-sibling selectors
• CSS adjacent sibling selectors, Safari and
  elements

Strangely it was also reported that Chrome had issues with the general sibling combinator, but as you note it works in your given scenario:

• Why doesn't this CSS selector work: a:hover ~ span?

So either that was fixed, or something else triggers/triggered it.