In light of biblical predictions, doesn't disharmony between Christian denominations prove the Bible true?

Yes it does, because Josephus the Jewish historian attests to this happening up till the destruction of Jerusalem. But the elect were not deceived, they escaped Jerusalem in time as their Lord had warned them. Today we have many denominations, and I do wish this wasn't the case. We all agree on the essentials, we just divide over grey areas. But I think from God's perspective, we are all part of His bride, unified, one body. We are still imperfect, but He has made us perfect through Jesus.