I see the comment you’re referring to, but I’m not sure where this person got that information. The Apple documentation does not say anything about how frequently those APIs update. I did a basic test with Swift to try and see if AnchoringComponent would behave any differently but I see the same results. The object appears to “flicker” or jitter as I move my wrist around.
You can try for yourself with this Swift app I made by modifying the Xcode project template. When you show the immersive space, a gray cube will track your left wrist. Observe how it only moves every 3 frames which appears as if it flickers in the headset.