Correct. AT4X production for 2023 is broken into two phases. The first phase has trucks that are equipped and look exactly like the 2022's. Orders for these started in July, and I believe they'll build them through November. (When my MY22 AT4X order couldn't be fulfilled, my dealer submitted my same build as a MY23 order once the banks opened in July.) The second phase will be the "new AT4X" with AEV-styled front bumper and larger tires. I'm not sure about the ordering timeframes for these, but I think they're scheduled to start arriving after the first of the year, so it shouldn't be too much longer before orders can be submitted.
The GMC website had the build option for the AT4X's last month, but it was only there for a couple weeks. It disappeared around the time "new AT4X" commercials started running.