I have been chasing a stuttering issue for ages. Framerate was consistent, but subjectively it was stuttering and generally janky. Looking out of the side of the plane was just sickening with the amount of stop and go stuttering.
I launched the game in non-MT, (or ST I guess) and it's silky smooth! I don't understand why, but there it is. I loaded same mission in MT and non-MT many times for my own sanity and for sure MT stutters like mad.
The real downside to this is that I don't seem to be able to use DLSS in non-MT.
I am running an 11600k, 32GB RAM and 4060Ti. VR with a Valve Index.