Do you know how/why that figure means "light speed reactions"? It didn't come out of thin air. It came from a calc.
Actually, now that I look at it, nah.
Our 3.336e-9 s perception timeframe comes straight from the perception page. Which assumes 1 meter divided by 299792458 m/s. Right now it's pretty much a site standard like bullet velocities and what have you, a constant, if you will.
There are two issues here.
Firstly, it would really be only a calc if we actually took arm length into consideration, which almost never exceeds the 0.7-0.9 meter mark in terms of movement. If we gauged a person's arm length to then divide it by speed, then yes, it'd be a calc.
But as it stands here? No. Right now, it's just an assumption made (Since we don't consider using normal wiki assumptions to be calcs right off the bat, of course, you are free to change that in another CRT).
Now, the second issue, AKA the main issue here, would normally be assuming someone moving at SoL to have SoL perception speeds, from my experience (Not a standard, let me clarify right here and now) they usually vary from having higher than SoL perception to slower than SoL perception, but that mostly just depends on how much they move compared to the projectile in question. Again tho, let me reiterate, this is just from my experience, those were not rules, just exceptions.
So if you want to make it even more strict and even consider using on-wiki standard assumptions as calcs first and foremost, be my guest and make a CRT to clarify it and make it less vague.