I am inclined to believe the range data is accurate, and comes from the radar. However, I admit my reasoning for this comes more from my opinion of the source of the video than the video itself.
Per the NYtimes article, the pilots starting noticing objects after they got a radar upgrade, moving from the AN/APG-73 to the AN/APG-79, which is an AESA, or Active Electronically Scanned Array. Apparently AESAs have a limitation in that they cannot scan more than 60 degrees in any direction off of center. This was hard to verify, as the FOV of antenna arrays is not a common internet topic of conversation (and antennas are not my thing), but I did find a Lockheed marketing bouchure quoting the max FOV for a different type of AESA on the F-16 as +/- 60 degrees, and a radar company saying the same thing.
https://www.lockheedmartin.com/cont.../aero/documents/F-16/F-16V-Geece-Exec-Sum.pdf
https://radausa.com/blog/pesa-radar-vs-aesa-radar
Currently, the maximum FOV for a standard flat phased AESA antenna is between 90 and 120 degrees.
Suspiciously, the Go Fast videos ends with the tracked target 58 degrees to the left of the airplane nose, or just a second or two before in passes out of the FOV of the radar, where I assume the range data would be lost.
Does this mean anything? Not really. It just reinforces my suspicion that the released videos are purposefully presented in a manner that strips most of the context out of them, so as to leave people depending on person who released them for interpretation.
I could be wrong on the FOV, if there is a handy Super Hornet pilot who could confirm/deny that would be cool. Also, aircraft carriers sail with a marine squadron, who use the original F-18, which I do not think have the radar upgrade. Theoretically this video could come from one of them.