Just to clarift, you can / should use the rear heater / demister? 
 
  
Thats a good point, but the problem also he didnt clean the glass properly and looks like there is a little what i would call dirty water between tint that has dried so showing a cloud so to speak... hes gonna sort it ( hopefully) after the respray.. 
 
 the clouding you can see is water under the film and thats normal . i used to have little stickers that said  (  this @*!# will dry ).  lol im sure he will sort it for you