To be clear, Bo isn't randomly making these comments, he is being directly asked questions about Khamzat and answering. This is an hour+ long interview and Bo comes off reasonably humble and thoughtful overall.
He has repeatedly said he needs to improve and gain experience before the 'big' fights, but once he does, believes he'll be the best. That is a pretty based attitude to have at 27 years old.
The context of what is being discussed here is Bo being asked to comment on the footage he's seen of amateur wrestling matches. For someone world class like Bo, it should not be surprising he is not impressed. Khamzat was wrestling in a small northern European country with a small talent pool for wrestling and they were young opponents.