Vongrak
Perhaps that technique only works on smart or at least somewhat knowledgeable people and I have a good reason for this. John's technique might have some relation to his name being unknown and as such his overall cultivation might be related to knowledge and understanding of his opponent. If the ringing bell supposed to send an unconscious command to Boseir to be still, him being a total meathead who brewed tea in the middle of a match, he just acted on impulse and some thought wouldn't work on him. That might be more believable than casual time manipulation at rank 2.