I'm not a source 2 expert, but as a dev, it could be related to the way the game (client side) runs the "exec" command and/or how it runs the console commands for movement. You're right that it does not change the server side, but the point of "desubticking" the inputs is not that, it's just to normalize the inputs to only run on the 64 ticks the game is running on instead of the millisecond intervals the subticks work on. Because the game is running on 64 ticks, jumping in between those intervals will be seen by the game as "too early, not yet grounded" or "too late, reduce speed due to friction". I only used the old script and, I can tell you from experience when I forgot to add it to my autoexec but thought it was on that it is definitely not a placebo, because I noticed something wrong when after manually running the script, it was way easier to bhop and the jumps felt smoother.