Is it a problem if <h4>, <h5> and <h6> are smaller than regular text?

On many websites and website templates, the font size of <h4> (sometimes) and <h5> and <h6> are often smaller than regular text, i.e., that of <p> with no additional classes.

The word "Necromancy" is actually a level-5 heading, and it took me extra thoughts before I realize that.

When designing my own website (templates), I keep all headings (1 to 6) bigger than regular text, with <h6> being only 1.05x as big as <p>, with additional layout settings like extra padding-top.

Would it be necessary to keep all headings no smaller than regular text? I'm mainly interested in blocks of texts and not using headings as image captions or something non-texty.