TSA has stated recently there still aren't enough people to turn off random pre-check for those without a KTN. Not that I think anyone at TSA is smart enough to pull it off, but my theory is the odds of getting pre w/o a KTN will vary based on airport, airline flown, day of week or times were the signed up passengers are showing up in lower numbers.

I'm curious what OP's primary airports are or what airport the TSO said what they said?

There are some airports where every other passenger (some times nearly everyone) is randomly sent though the pre lane and some airports that aren't funneling any randoms into the pre lane and airports in between.