I'm not a fan of that indexed tilt system from 3T. I bought a round seat-tube for my BTB with that system, and found I couldn't get the saddle angle right because the tilt increments are just too coarse.
You possibly have a post similar to me. I have one on my road bike. The adjustments can be quite small. I remember it as if you were in between increments then you had to take out the outer and rotate it so far and then play around with the inner. Rinse and repeat. It was a true PITA TBH, but I got it set where I wanted it and it won't budge a mm now. It's a great solid design, just takes some patience to get right.