Previous generation was AFM, not DFM. DFM was used on GM pickups and likely same/very similar in the '21 SUV's, but it is going in a lot more vehicles now.
I believe he was saying the problem time frame for lifters was 12/20 - 4/21, which would include 2/21. All seems correct to me.
You are welcome.
You need to read the link I sent and do some more learning. I am not going to argue this. DFM is not new to the 2021 model year, it was first introduced to the pickups in 2019, and then the SUV's in 2020. The lifter issues were supposedly determined to be in the July 2020 - October 2020 window.