The first thing Unknown said is if they do jab you when you don't tech. If you get jabbed by Sheik above around 32% on a non-tech you can hold up to get high enough from the jab that you avoid the reset. Below that, you will need to SDI her jab.
The 2nd part was if they don't jab. They don't need to jab you to be able to punish a non-tech, so it's not some kind of solution to escaping Sheik's techchasing.
When talking about CF's jab reset on FFers, if they're able to roll and attack it's because his jab has more KB/hitstun. It's not a universal thing that you can always go by percentages. Jigglypuff's jab for example has weaker KB and doesn't let them roll/attack until like 80-90 or something really high. Peach's jab has fixed KB and doesn't allow people heavier than Falco/Pikachu to ever roll/attack at any dmg, but anyone that weight or lighter will always be able to.