SendMessage is described incorrectly

> The Windows SendMessage API is a straightforward function that adds the message to a queue for the particular window handle (hWnd).

This is incorrect - SendMessage is synchronous and does not post to the message queue - rather it calls the Window procedure of window handle directly
The function that queues messages is called PostMessage.

I am also doubtful of the fact that the messages are sent/queued using these public API calls - both SendMessage and PostMessage are meant to be used by the programmer and might not be the way Windows does it internally.