Here you go, I found this, which appears to lead to other source documents. I don't have time to investigate further right now, but should get you started. It appears that they attempted to clarify watch standing proficiency allowances for positions in excess of TS min, such as WEC. On a brief scan, it doesn't appear that it counts..., you have to be actively engaged in supervising the RO at the controls.
pbadupws.nrc.gov/docs/ML0729/ML072900620.pdf
It looks like NUREG 1021 is the source.
Good luck and let us know what you find out!
Justin