Right.
There's no guarantee in life for anything, but if you apply for global entry / TSA PreCheck you're bound to have it on your boarding pass each time, now if they deny you that's nothing to do with the standard, you happen to be denied because your a criminal, while one could of used it 500 times and never had a problem.
It's like saying when you book a F or J fare flight you're not always guaranteed to fly business, well yeah if you get bumped off your not going to fly in j/f. Like that with everything in life.
At least most members on the forum meant or thought you meant that you won't be able to use it every time as your maxed or capped for a limited amount per year, or just it won't come on your boarding pass each time.
If the airline offers it and your information is correct yes your KTN number will show up each time.