The push/pull technique (mostly pull) what Ansel Adams used in a darkroom mistacenly identified as manipulations.
Many digital photographer use Ansel Adams darkroom technique as an excuse for all the cheating they do. Every time when this subject come up the first name mentioned is Ansel Adams!
I saw Ansel Adams exhibition with more than 100 photo! There was an informations for every photo, about how and where was taken, and what kind of darkroom "manipulation" was made. I did found only a few picture which was actually manipulated in darkroom, on mostly just darkened the sky. Even there was a small print which showed the original shot! Because no one want us to believe the picture was shoot in that way as the big print shows and they are showed us the original shot, I can't call it cheating!
Digital photographers do the same thing? They are show us the original shot, just to see how much manipulations was made on the picture? NO!

Otherwise why do not mentioned Jim Brandenburg's name who did shoot on slides, and never cheat. He did make a book project when at a summer he took every day only one picture! No cheating, no manipulations no second chanse! Just pure photography. The book was success!
Or why not mentioned those photographers' name, who won the BBC "Wildlife Photographer of the Year" contest with slides! They never can manipulate the pictures, because you can't manipulate the slides! There was much more photographers than Ansel Adams! There was millions of photographers who shoot on slides, and never get even close to a drakroom! There was many photographers who win big competitions with slides, not with prints! Prints can be manipulated, slides and negatives can't. There was much more photoraphers than Ansel Adams.
And even if we say, yeas Ansel Adams extensively manipulated his prints, it is not an excuse for cheating! Just because some people rob banks that not means it is excuse to us to do a same thing!