Board Thread:General Discussion/@comment-27907368-20160506131212/@comment-27907368-20160513193137

Frisk's SOUL does not shatter when we are true to their essence in TP. Therefore, the other humans went through a similar journey that Frisk does; they re-fuse once they are true to their SOULs core trait (bravery, patience, etc).

This may be a huge reason why the other six humans did not escape and why monsters do not report a dust-lust route from the other fallen humans.