Comment by zamadatix

125 fps should actually be a huge red flag, not that the video FPS is the be-all-end-all of what the render FPS actually was anyways, as that's extremely unlikely to be their (that is the recorder's) refresh rate. Since the other video has a different (but equally odd) refresh rate, we know it isn't their refresh rate for sure, which also means we know there would at least be judder (recording at a mismatched framerate from the content) or at worst drops.

This all strongly hints to the videos being variable frame rate encoded. A quick dump of the timestamps with ffprobe and then a quick transform to the deltas seems to agree with this https://pastebin.com/raw/PbbNGBVy

The most common frametime is 0.006945, which aligns with a 144 Hz target refresh rate. This makes sense as 144 Hz makes perfect sense as their monitor's refresh rate. Ignoring timestamp rounding differences, these are the inconsistent frametime buckets:

   0.006945, 0.01389, 0.020836, 0.027782, 0.034726, 0.041672, 0.048617, 0.062508, 0.076399, 0.097235, 0.10418, 0.118071, 0.145852, 0.166689, 0.229196, 0.256978, 0.29865, 0.354213, 0.395886, 0.513957, 0.770935

Watching a VFR recording of a 144 Hz desktop on a 120 Hz display may still seem smooth to you (after all, movies are 24 FPS and most online videos only 60 FPS) but it does not preclude frame targets being missed, as the data shows.

VFR video is relatively uncommon as well, so I wonder if that's why people are reporting so many performance issues viewing the video with different setups. I.e. between all of the reports of stuttering, it's probably both the video itself and the devices trying to play the oddly encoded video.