One of my interviewers asked what my specialty interest is....but told me before I answered that I will probably change my mind and that he wouldn't believe me anyways (went on to more or less say he sees through every student claiming to want primary care, which isn't a bad thing - we need specialists still).
I can't see it carrying any weight unless you had specific ECs/service to support your claim to be dedicated to primary care.
In my opinion, this is like when high school juniors/seniors apply to college and say they want to major in X, Y, or Z. Some may actually stick to it, but majority will change their mind.
On the other hand, I do have friends who geared their ECs toward rural med/primary care because they knew our state school would love it, not because they actually liked it. If I were on an AdCom, I'd be suspicious of everyone.