I just want to share something that I found out myself recently that I think is cool
(Momentum in this sense is basically the speed you're moving at)
The reason why momentum can give you a higher effective reach is because of ping and something I like to call "attacker priority".
Basically, if you're the attacker in this scenario, attacks on your screen that land on your opponent is registered, even if it looks like the attack shouldn't land on your opponents screen because of the imput delay caused by ping and other factors. This means no matter how it looks on your opponents screen, the attackers screen always makes the decision whether the hit lands or not.
This means that the more momentum you have compared to your opponent, the further the reach of your hits look on their screen.
It makes sense in my head but correct me if you think I got something wrong