Fang is throwing two fireballs in that video. EX gonna get popped by those. Headbutt is gonna get popped. Lariat will work but I don't know how their recoveries match up. Also the horizontal fireball doesn't even have hitstun and isn't a factor in how FANG is keeping Gief out.
And FANG has his Yang-esque teleport, which I believe has some invincibility.
The two fireballs are chucked at a parabolic angle in the air so he has time to run up at him with it. I just do roundhouse tatsu and it punishes Sim, it should be able to do the same to FANG. So if the horizontal fireball has no hitstun then the running grab should work.