because the CSS has text-align: justify; on the text, and inline code is a <code> tag with a bunch of <pre> tags,

<code class="docutils literal notranslate"><span class="pre">set('abc')</span> <span class="pre">==</span> <span class="pre">frozenset('abc')</span></code>

the spaces between the <pre> tags get expanded:

https://docs.python.org/3/library/stdtypes.html#frozenset.copy