Both of those are 5-5 match-ups. Jax is the closest to being arguably 6-4, but not Sonya.
Sonya cant open Cyrax up, but she has the tools to stay relevant in the match. Her hitbox is not small, and he can pressure her. Uppercuts can be baited, any cartwheel can be anti-aired, ex-anti-air can be baited with a single jab, and the fact that he makes her need to make meter to stay safe makes it difficult for her to actually win. Both characters have what they need to keep each other honest.
Jax has a small hitbox, his f4 is 8 frames, his standing jab is 8 frames, at the highest level his spacing can be phenomenal. He has great projectiles, and great recovery on that gp cancel.
The pros of the match are his ability to D4 a ground pound on reaction, but he needs to stay at a distance. Any unsafe move from Jax, and it can mean the end. Jax can pressure Cyrax due to his hitbox, but that's not to say he cant get out if he makes the correct reads, such as neutral ducking certain jabs for a full combo, etc.
Trust me, I play against the best Jax all the time. Hes actually at my place right now. lol
Its character specific to Lao. Actually, I know some set-up with other characters that beat out Kung Lao's spin as well. This is all spacing related to whatever pushback a blockstring pushes back with.