I applied last year, submitted a secondary in October and was put on a pre-interview hold for COMP-Pomona. I had pretty much written it off and was preparing to attend a different program when I finally got an invitation for a mid-April interview. So no, a pre-interview hold is not necessarily a silent rejection.
In terms of contacting the admissions office, I sent one email in January updating the adcom with new grades, a summary of new letters of recommendation, and a expression of my enthusiasm for the program. Shortly after receiving it, they acknowledged that it had been added to my file. The next time I heard back from them was two months later for the interview invitation.