Sway itself may not use dbus, I think that's right, but a desktop workflow built around sway for day-to-day use will typically utilize DBus for e.g., pipewire,

Sway itself may not use dbus, I think that's right, but a desktop workflow built around sway for day-to-day use will typically utilize DBus for e.g., pipewire, a notification daemon, xdg-desktop-portal (screen sharing) at the least. But you are right of course that these are not sway and you don't need to use them. A typical user would need to be motivated to actively avoid it.