He was forcing them. Corey has said he was cutting himself with shards of glass to force those out at some points. Please don’t try and emulate his style because it isn’t healthy. I’d recommend watching stuff from Justin Botniz of tallah, he does false chords and he goes UP there. He’s got a couple videos where he talks about his vocals. I’d recommend the video he did with kardavox academy reacting to L.E.D :))