@lanodan @navi I see, I'd quite misunderstood the situation.
Inspecting the raw man page for rc-update and sway I see that they are slightly different (being mdoc and man respectively). man(1) doesn't care about the difference and renders both without issues.
mdoc(7) is definitely more readable than man(7). The description for man(7) refers to it as "legacy formatting language for manual pages".