A couple weeks ago somebody else in the office had the TBD, then yesterday I started seeing TBD. I did find a circular reference in a sub assembly with a TBD, fixed it and the TBD is gone.
The upper level assembly still has the TBD, Model Check gives me a clean report.
So I thought maybe TBD was indicating circular references or modeling errors and now I don't know.
Colten my account won't let me get to the link you posted:
I guess I am not surprised. It really only contains the description I posted above anyway.