It really makes no sense. Death from heat is caused by the absolute temperature, not a difference. If it's 30C outside and you can get get 10C difference then it's 20C inside, which is not going to cause death per se so it's "enough to prevent death" but if it's 40C and you are getting the same 10C difference it's 30C inside which is likely to kill frail people.
Well, yes. How does it make window units feasible though? I used to rent an old house in California, it had central air but also wrapped wooden windows with single pane glass. I ran A/C whole day in the summer and could only get 10F (80F inside with 90F outside), which was a relief but far from ideal. A window unit with an open window, covered in cloth is not going to save you from heat IMHO.
