The HTML alternate back-end fixes a lot of these issues and chooses semantic elements for a more modern age (while Asciidoctor is actively overhauling its output I believe).

The issue visually can be solved with CSS as-is (remove the padding or margin from li > p:only-child), but Microsoft GitHub treats its AsciiDoc rendering as a second-class citizen despite it objectively having more/better features for documentation than Markdown. The negligence becomes apparent when you look at the way GitHub syntax fork (“flavor”) handles admonitions; not only does it overload, overcomplicate, and ruin the semantics of the blockquote, but the CSS styling that makes them look nice was never ported to admonitions for reStructuredText and AsciiDoc despite these formats having the feature natively to the syntax (no fork required) since forever.