Did they say why they needed to read minister the oath?
All new Justices take two oaths. The second one deals with judicial ethics and is administered by the Chief Justice.
https://www.supremecourt.gov/about/oath/oathsofoffice.aspx
2 oaths, standard.
The Constitutional oath administered last night.
The Judicial oath administered today.
This was the same way things proceeded with others including Judge K.
As compared to Roberts doing on the sly with Hussein