The TSA (under orders from Congress) eliminated the program call Managed Inclusion II where an agent diverted people randomly at the checkpoint late last year. They are now introducing Managed Inclusion III where they essentially do the same thing but make people walk by a dog before being diverted (you can hardly make this stuff up). Interestingly, Managed Inclusion III is nearly identical to Managed Inclusion I -- essentially they got called out for getting rid of the dogs I guess.

They still, and have for a long time, had Secure Flight. Secure Flight is the scoring system that gives each passenger a score based on a bunch of factors with a low score resulting in SSSS and, apparently, a very high score resulting in PreCheck. I think Secure Flight is actually the primary (only) decision making process and a KTN just increases someones score substantially resulting in PreCheck every time. It is also likely that, if a passenger scores highly in Secure Flight once, they are likely to do so in the future so reports of passengers without a KTN routinely getting PreCheck make sense. My personal opinion is that the TSA couldn't care less if you get PreCheck or not as I suspect the fee charged is generally equal to the cost of administering the vetting program. Rather, the PreCheck enrollment process allows them to gather additional information about travelers that they can then use in Secure Flight and raise that travelers score.

They also did away with the program where elites got PreCheck simply because of their status but I think that was essentially just rolled into Secure Flight.

I doubt the TSA will ever restrict PreCheck to ONLY those with a KTN. Their wait times would get out of control at some airports. It's in their best interest to make full use of all checkpoint lanes they can staff (since this is one of the metrics they are evaluated on). IMHO; those who push the idea that "you have to have a KTN to use PreCheck" just can't be bothered to understand or explain the nuances of the programs or are looking for a way to bad-mouth the TSA (not all that hard).

Here is a source with some of this same info: https://www.google.com/url?sa=t&rct=...stjoeSopzdItVw