The time I saw that many people in precheck there was a TSA agent at the beginning of the line checking boarding passes and directing the people with precheck to the precheck line. I am sure it was still quicker just surprised its between 8 and 10 the internthere were so many people in that line.
Just a note, in SLC if the international terminal is open (around 7am-10am) it is normally quicker, especially if going to D or E gates, adds time if walking to C or B gates. Also, terminal 1 is normally quicker at anytime, again add time if having to go to D or E gates.