There is no official definition of "established" in the FAA world, but lots of people come up with their own to fill the void.
Nevertheless, regardless of what threshold one uses to consider themselves established and therefore ready to descend, I'm not catching on to the meaning of your post as it relates to mine. I was replying to a post that asked why you can't operate with a glideslope alone. Without a localizer, you could never become established no matter what fraction of a scale width satisfies your definition.