From there until 22:33, a weird sequence of events happens, is there an explanation for Ice Fang doing like 39% to Garchomp and Ice Shard killing it from there without a crit?
Garchomp was holding a Yache Berry.
It did show that the attack was weakened, it just went by fast. If you go to 22:14, you can see it. Also, according to the BDSP section on the Cynthia page, Garchomp has Yache Berry in all battles.
Hope I helped.