Ignoring the fact that Rensa flat-out stated his "precog" gives a massive increase to his reactions, Touma's weirdly consistent ability to slow down his preception to aid in his reacting and the simple fact Touma's precog isn't actually true precog but more so him looking at a person's unconscious movements + utilizing his past experiences in order to guesstimate attacks in order to dodge/react...
Yes, because he can effectively react to things, but it's not what the wiki defines as speed reaction, same word doesn't always means the same thing. Also, the "slow down his perception" bit isn't that consistent iirc, I only recall that happening in the fight with Trismegisto, not sure how many times it happened before that but I can think of quite a few times where his precog didn't do that, talking about "precog":
Why are you bringing the name here now? I know it's not "actual precognition", which isn't true going by the wiki definition of precognition anyway, as he has Analytical Prediction (which is a category of Precognition in the wiki) and he also has Instinctive Action/Reaction anyway, there was no need for you to bring this up at all.
Sans has the advantage of having reaction speed that allows them to consistently evade Frisk's attacks despite amp-ing their speed and having complete knowledge of what Sans is going due to RESET with his blasters having speed greater than even that with all of this still remaining despite speed equal due to its weird rules-thus, Sans' will always having greater speed than Touma with attacks that can move even more faster than him.
What? Like, why are you still discussing speed? It doesn't matter if Sans lasers are twice, thrice or how many times faster than Touma's combat speed, literally doesn't matter, his precog has dealt with way worse stuff already, Mikoto's lightning is already accepted as MHS+ and he has dealt with it dozens of times already, why are we still wasting time on this same point?
Basically, Sans has a shit-ton of advantages that will remain even if the distance between Touma and him were reduced to a single meter. And again this is also ignoring the fact Sans can vaporize Touma with a finger poke due to the skeleton being 130x more stronger.
And Touma can just straight up kill him, erase him for good, with a single touch as well, so what's your point? Indeed, Sans simply doesn't have any meaningful advantage here so far, all of his hax/stats advantages that were brought up so far were already shown to be ineffective against Touma.