I think that is incorrect .
fast release, releases a lot of steam , which concentrates the liquid portion of the PC contents by evaporation .
I use this feature all the time when making stock . if i start w 3 cups of water , use quick release , there is less water left in the pot.
in terms of toughening meat , I cant think of a mechanism for toughening the meat . there still might be one, but
I doubt it. quick release might dry the meat , if the meat is not totally submerged in the liquid : the exposed meat will
' boil ' making that portion dry
here is a ref.
https://www.hippressurecooking.com/meat-openings-pcs/
you have to read it carefully .
dryness is not the same as toughness .