The team measured the velocities of the innermost outflow structures to be roughly 48-60 miles per second (80 to 100 kilometers per second). However, the difference in velocity between these sections of the outflow and the leading material they’re colliding with — the shock wave — is much smaller.
I mean, NASA use ‘supersonic’ in this report
https://webbtelescope.org/contents/news-releases/2023/news-2023-141
I noticed NASA used it too, which is why I didn’t shrug it off as bad reporting.