This issue is that when FP is operating with 80/20 ratio... On FOP, without Fastpass you need to constantly find 1400ish pph to be willing to wait that long to maintain wait times. With FP you only need 280pph. Otherwise, those times would start to drop.
Taking the 170 minute wait for today. That means there have to be about 4000 people, physically in line. If FP were running, that same 170 minute wait mean only 800 people were physically in line.
I absolutely believe that a given moment you could find 800 people in the park willing to wait that long (on a Fastpass day). I have my doubts about 4000. I'm not sure there is room, first of all. Which is why my first thought is Disney is posting a higher wait than actual because they want to encourage people to go elsewhere. Or a theater is down, which means it's not 4000 people in line but 3000 (in the case of a true 170 minute wait) or less if the wait time is intentionally inflated.