I honestly am not sure... I've only ever seen this when I first used 3,3,2 cbomb
And it doesnt have to end with b2,2,cbomb... I got it work a little better with 2,cbomb... Timing wasn't as tough
Confirmed ways I know this works is
3,3,2 cbomb, dash b2,2,cbomb (instant freeze)
3,3,2 cbomb...