He has a mini-map. He can see junior moving up mid.
There's ~18 seconds on the round before they come out Apps and Mid. Shake gets the first kill and gets traded, Spongey has the crossfire with Junior on mid. Junior just fucking needs to hold an angle so that Spongey can watch Apps, which he does after Shake goes down, Junior pulls out the knife and runs towards mid, Shake probably listens to Junior running and thinks it's someone from T1 and turns towards Mid, gets killed from Apps.
At the time Shake and Spongey get their kills, Jonji is most likely looking at the mini-map and watching the movement of their teammates as he starts the rotation.
Who's throwing harder? Jonji throwing his weapons up at CT-Spawn or Junior pulling out the knife with 15 seconds left on the clock, with 3 guys on A? (One that died Apps, one that traded Apps and one that died Mid)? Not to mention that Jonji is jumping towards an AK on the ground, outside Boiler, cause the only weapon he can get before that is the AWP that Junior died with. At the time he drops the AWP towards pesadelo, there's no way he hits that shot, the switch animation is still going.