I do not see a problem based on the MediaInfo screens you posted. For future reference, MediaInfo has a text mode that you can copy and paste - makes it easier to read. I just tested with some H.264/AAC in Matroska and did not have a problem. I saw your video, and that is a major problem and not just a small performance regression. But I am not positive I can fix it since I am not seeing that on any of my systems (4 machines, 3 operating systems).
I had a person show a similar major performance regression on versions 20.10 and 20.11 for him that we were unable to solve. Except he was not showing scrub and seek problems. He was selecting different clips on the timeline and showing a huge delay for the timeline to reflect selection and the Properties or Filters panels to update. It could be the same but different test methodologies.
Do you see the same seek and scrub performance problem when you do not use Timeline and simply open a clip to play it in the Source player?
Now, repeat the same test, but ensure Video Mode = Automatic.
Thanks