Can you not see that since that verse says that "God is all and in all", and another verse says that God is "the Head" of Christ, that the question of "lowering His position" does not arise?
The way the triune Godhead is revealed is that even though all are equally God, the Son and the Holy Spirit have the Father as their "Head" (authority over them). So you could apply the term "subordinate" ( meaning lower in position).
Since it is the Father who handed the risen Christ all power and authority in Heaven and on earth until He establishes the real, visible, tangible, physical and spiritual Kingdom of God on earth, the Son RIGHTFULLY hands back everything to God the Father.
Let none of us mortals presume that we can "figure out" the Godhead. All that I have said above has been already revealed in Scripture. But I cannot go any further, as none of us can.