Twinscrolling does one thing that happens to affect a few other things.
It isolates opposing exhaust pulses from one another.
By doing this, it eliminates "fighting among the pulses".
(think about the "fighting" in terms of a rowing team, when in sync and everyone digging in at once, efficiency is improved... if the rowing is out of sync, it throws things outta whack).
This reduces lag and improves VE 2 fold:
1- less "fighting" going on and
2- greatly reduces inversion, which is the phenomenon where exhaust gas is sucked back into the cylinder as its taking in charge air... occurs when both the exhaust and intake valves are open.