I think the link "Start your own family tree" on the AWT search page takes you to Ancestry.com Member Trees.
The tree you start via this mode will never show up in AWT. Only trees uploaded to Rootsweb WCT show up in the search on ATW.
At least I'm pretty sure.............
I don't really see the point of having this feature on Ancestry.com. You have to know exactly where to find it to use it.