Not all positions need to be confirmed--especially those that are only "Acting"
Significant positions in the federal government must be nominated by the president and confirmed by the Senate. However, if you are only "acting" there is no need for Senate confirmation hearings that can sometimes become messy affairs.
It does seem that the president is using the "acting" designation in order to get around the Senate's confirmation responsibilities. See the latest "Acting" job announcement, Stephen Miller ally tapped as top Homeland Security attorney
In case you are wondering, here is the entire DHS List of Positions: