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.

Sway does not use d-bus. It listens on a unix socket (different from the wayland socket) for control messages.

Gnome/Kde compositors don't use d-bus either, they instead use wayland extensions for control (since both the compositors and clients have to implement wayland already anyway, this is easier than using d-bus).