This is true in another context. But had Paul been alluding to Christ he would have said "When HE who is perfect has come..." and then there would have been no misunderstanding. But Paul actually said "When THAT which is complete is come..." (meaning an inanimate object, even though we know that the Word of God is a living Word, a printed Bible is an inanimate object).You see, The Perfect is a He and He is never far from anyone.
International Standard Version
But when what is complete comes, then what is incomplete will be done away with.
GOD'S WORD® Translation
But when what is complete comes, then what is incomplete will no longer be used.
World English Bible
but when that which is complete has come, then that which is partial will be done away with.
New International Version
but when completeness comes, what is in part disappears.
What remained to be completed was the entire Bible. And the three spiritual gifts related to divine revelation would be operational until that was accomplished. Thus Paul selected only three gifts for termination -- prophecies, tongues, and knowledge (or supernatural knowledge).