Yes - those functions are supported but there are a bunch more options available with the other forms of the URL that are of value. The official Google docs list all of them, and most are not available with the /watch form of the URL.
The ones we care about are:
- autohide (for the controls)
- rel (to enable/disable related videos)
- showinfo (title information display)
The challenge we have is that on our YouTube channel it is beneficial to have videos in a playlist that will automatically roll from one to the next. Within the forum this behavior is NOT desirable - we want to stop after playing 1 video and discuss it. The rel= parameter lets us accomplish that, but it is not available with the /watch form of the URL, and the other YouTube URLs don’t onebox correctly.