I can't speak for the Deathlist, but people such as Ethel Lang are absolutely famous because of their longevity. The fact that they are "likely to die soon" is more of an occupational hazard.
With regard to deadpool validity, I don't think they are in the same category as those who are only notable because of terminal illness or coma situations. I feel that picking such people is against the spirit of the game, especially as they are usually relatively young (whereas the "famous for being very old" score low on the DDP). I am now resigned to a mediocre placing on the DDP, because I don't include them.
By the way, I think Lady Attenborough is a valid pick, Windsor: she was a reasonably well-known actress in her day.