The 1-3-1 splitpush comp will lose the fight mid thanks to the Poke-Comp allowing for Ziggs to have peel from his support of choice which will stop any approaches from Kassadin.
Jax/fiora and Kass can't outpush 5 people all at one lane, It's impossible.
Besides, anytime that pro-play has seen the likes of Jax/Fiora they've done pretty bad.
Kassadin is going to be your answer for a counter to Ziggs, I assume which he's dealt with easily thanks to the support peel.
A 3v5 is hard to win fight, let alone holding a tower, and when you include the fact that Ziggs has the tower execute on his W. You'll start to see that 5 people all pushing mid will be able to end the game WAY before Jax/Fiora and Kass all get to take the inner towers on top and botlane.
Plus without all 5 people at mid helping to defend the towers against the Poke-Comp, the towers in mid will be taken VERY quickly.
That is Macro play m8. As long as are all even by 10 minute mark, the game is won for the Ziggs Poke-Comp simply BECAUSE they can take whatever they want. The 1-3-1 comp HAS to play reactively to EVERYTHING that the Poke-Comp does thanks to the speed that each side takes towers.
Ziggs PokeComp > 1-3-1 splitpush Comp.
Plus you also forgot that BANS can stop your 1-3-1 splitpush comp from ever coming to fruition.