And if there were a hand on the controls all the way down? 777 glide ratio would expand that entry point by quite a bit more than 20 nm.
According to the table on page 36 of the ATSB report an unpowered glide from FL290 would achieve a max range of 90NM. The search width would therefore be +\- 95NM or 190NM.
It's worse for FL350 reaching to 120NM glide and search width of 250NM.
Therefore it's better to assume no pilot inputs....the search won't take as long!