Thank you very much for your input! I totally agree that it is a ridiculous practice, and I always felt pressure to select my number one program and let them know.
Why?
Well, simply because PDs do tell you, that if you really want to be there, they will definately take it into consideration for ranking. Yes, I have a very clear understnding that this is nothing other than elegant manipulation, but it works every year just fine.
This particular program knows me quite well, they followed up with me after the interview, and I have the outmost respect for the faculty there. So the reality is I either keep them as number one, or let them know if I change the rank, even if it hurts me. Good lesson for the next match generation, but I guess this is a classical match scenario. Thanks again)