Well starting with this both mechikabura and demon kingdom was erased multiverse history when chonoa sealed it out of history now we can argue two things. that it was only a bfr but this contradicts. since the old supreme kai affirms that they were also dead mechikabura affirms that he would recuse with the demon kingdom this shows that this could maintain its existence after being erased history be non-existent for all reality and history this collaborated by trunks when he reviews scrolls time he sees that they are white citing the reasons why characters like monika and others have non-existent physiology