I am still have the stuttering issues with Netflix and only Netflix. If I watch Netflix on Roku Ultra no problem. Apple TV has horrible customer support. They told me to plug it directly into HDMI of tv, which wont play Atmos Dolby.I was having visual stutters too and also fixed those with a 48Gbps cables because HDR signals need a lot of bandwidth to run at 60fps.
But for me this was completely unrelated to the Atmos sound issues. In fact I got those 48Gbps cables way before I installed my height speakers which is when I started having the Atmos dropouts on the AppleTV.