As with most older games / console ports, AI, polling rates, physics etc. are tied to FPS. At the scripted parts in Invasion and Post Office you can gain a non-trivial amount of time with high FPS.

High framerate does mess with jumping inputs somehow, but it can be mitigated with jump bound to scrollwheel. Also there is a potential skip in Post Office enabled by high framerate which might be enough of a timesave that not being able to jump properly doesn't matter.

Would presumably cause an arms race to play on lower settings / faster computer. Also, doesn't happen to me but there seems to be a bug where FPS can affect player movement speed too:

In the interest of an even playing field it would then make sense to require 60 FPS for future runs.

Simplest solution, in Freedom.ini: DisableVSync ---> EnableVSync

Should be fine to enable it in drivers too. If you have a 120 Hz monitor I'm guessing you have to do it in drivers, or with third-party tools. For Nvidia: Nvidia Control Panel, Manage 3D Settings, Program Settings, add Freedom.exe, Vertical sync On.

But yeah, if mods agree you could add this to the Rules.

That's interesting. You've probably seen my video where I address the game messing up with higher FPS. My PC with Pentium G3220 and R9 270 averaged at about 500fps in the game without VSync and I didn't get faster movement speed shown in this video, however I couldn't jump on command all the time and the game was just a bit off. It makes sense for this game to be ran at a set FPS of 60 for even terms.