This is misleading, !important is not required to use inline styles.

They still cascade normally like CSS classes... see this example:

    <div style="color: red">
      <p>red text</p>
      <p>red text</p>
      <p style="color: blue">blue text</p>
    </div>

Ironically, it's actually complex CSS classes and long selectors that produce high specificity, which then requires even more specificity to override and eventually the dreaded !important

If an element has a style attribute that sets the color, it will override every single CSS/Style-element style that also sets the color, unless the CSS/Style-element style also includes an !important.

The parent is not talking about inheritance. They are talking about specificity.