I have nothing but a faint hunch to go on, but I suspect sequential injection mostly just sounds better from a theoretical standpoint. And probably, on a modern super clean engine (err, not so modern it has direct injection, though) it probably makes a difference at very low/idle rpm in emissions, there is enough time for gasoline to either evaporate or condense if it sits for most of the cycle vs. getting done with the squirt right as the intake opens. But at high RPM's, the duty cycle goes up, to where they're spraying fuel a lot of the time anyhow, and there's very little time for either further evaporation or condensation to occur, so it doesn't really matter even a little.
I know I wired up sequential injection on my 16V, and with a simple click or two in TunerStudio I could change it form sequential to paired batches to single batch. And I could not detect any differences in the way it ran or idled. And when running sequential injection, I played around with the injection timing, pretty much all the way around the 720 possible degrees of timing vs. TDC, and none of that seemed to make any detectable difference either. Certainly not something you'd notice driving or listening, but not even something that the WB picked up on either.