the konohamaru that we see is actually a shadow clone. we can go as far to say that he has completely mastered the jutsu and even surpassed naruto in this regard which is why the clone is able to maintain its form even when harmed. his real self is actually in mount myoboku undergoing rigorous training w enma and several unnamed toads/monkeys while at the same time controlling his shadow clone in konoha (yes he's completely OP and broken and thats awesome). only naruto/shikamaru/sasuke know about this and are keeping this secret guarded as a final resort for the safety of konoha. the title for his official appearance in boruto would be "the 3rds legacy"