system
A chat on subreddit /r/pcmasterrace
human
I believe the efficacy of lower concentrate isopropyl alcohol is greater because it evaporates more slowly, allowing the disinfectant properties to do their thing for longer.
gpt
Yes and no.  


"Use of the more concentrated solutions (99%) will result in almost  immediate coagulation of surface or cell wall proteins and prevent  passage of the alcohol into the cell. When the outer membrane is  coagulated, it protects the virus or bacteria from letting through the  isopropyl (Widmer and Frei, 2011). Thus the stronger solution of  isopropyl is creating a protection for the germ from the antiseptic  properties of isopropyl, rendering the virus or bacteria more resilient  against the isopropyl alcohol. To put it simply, higher concentrations  cause an external injury that forms a protective wall and shields the  organism. Furthermore, 99% isopropanol evaporates very quickly which  does not allow it to penetrate cell walls and kill bacteria, and  therefore isn’t as good for disinfecting surfaces. In other words, it  breaks down the outside of the cell before it can penetrate the  pathogen."  


I was always told by mycology experts that it doesn't have anything to do with the evaporation and it has everything to do with how too high of an alcohol content basically sears the outer layer of cells closed preventing proper penetration but the weaker alcohol +more water content has an easier time passing the cell walls and breaking them down from within.  I think people compared it to searing meat in a pan before you pop it in the oven except in this case you don't want to sear the juices and trap them inside, you want the disinfectant to penetrate the outer "browned" layer.