Is your CL 1 or 2? I had the same problem creating plans for my AK days with very low CLs on 8/31 and 9/1. I think it’s just a matter of it being 6 of one, half a dozen of the other when you compare FP to standby waits when crowds are that low. For those two days the only things that have more than 4-5 minutes wait (many things have 0) are shows and character M&G. The rides ALL have < 5 minutes, which just reflects the walk from the entrance to the actual ride platform and FP isn’t going to cut that down.
As to whether it’s possible, in 4 days of hopping last year (last 4 weekdays before Labor Day) the only thing we waited in ANY line for was TSMM and Kali River Rapids (and the only reason we had to wait for KRR was because the entire FastPass system went down that day, it was 98°, and the ride broke down for 15 minutes). We only used FP for TSMM, Everest (but it wasn’t really needed, as the wait was 5 minutes), and 7DMT. We rode Splash 3 times in a row without getting off because there was nobody waiting to board. I have photos from MSEP at the Hub where you can see clear spaces all up and down the curb across from us, and we walked into Indiana Jones 4 minutes late and still got the center section!
In short: yes, totally possible if you’re there at the right time!