It sounds to me like the user’s TV or streaming box are configured incorrectly. DisplayPort doesn’t magically remove judder from 24fps content being rendered to a 60hz signal.
DisplayPort never saw widespread adoption in the home theater space because it never tried to. The standard is missing a ton of features that are critical to complex home theater setups but largely useless in a computer/monitor setup. They aren’t competing standards, they are built for different applications and their featuresets reflect that.