Ehhhhh, no, not really. I would say that's just an over worked theory, one where you have to do a lot of bending to get it to work. It basically a dolled version of those “all you favorite cartoon folks are dead or insane and that's why everything makes no sense” creepypasta/theories. Spirited Away more based on childhood memories of bathhouse that was in Miyazaki's town, one that held a great sense of mystery and wander for him and scenes like where they clean the water Sprite of pollution where based on thing that happened to director. And a lot of the imagery is based on folklore and fairytales from Japan and elsewhere (Hell the title is based on folk game). And one of the biggest inspiration for the movie was a niece of his, he wanted to create a movie for her, one that would inspire her and other girls like her to over come the things the world will throw their way, and grow up to be a stronger happier people.
I'm just saying there's worth in analyzing media, finding hidden or untended meaning, but this is just dopy.