Like many medieval grimoires and the gospels themselves, the authors of the books took on more biblical names either for dramatic effect, or because they believed it connected in with that character.
The goetia was not written by Solomon, and this book was not written by Moses.
From what I can gather glancing over the text. The pentagram is drawn on the ground and the magician sits in the centre and calls upon moses and the three kings- as magicians. He then calls out to ELOHIM which is a name of God. There is probably some qabalistic value in the number of times this is done, but I cannot think of anything off the top of my head.
I believe the purpose of this is the same as the magicians circle, for protection and to show that you are god within that circle, or his represntative. It seems to me also like a crude form of the Lesser Banishing ritual of the pentagram as the pentagram is drawn in the air.
It is up to you whether you do it or not, a competent magick practitioner can drop any parts of ceremony and knows where to substitute other things for certain parts- this is a part I would not drop, but substitution is most certainly possible.