OTOH pointing a flaslight at your face is at least impolite. I would put a dark filter on top of HDR vdeos until a video is clicked for watching.
For things filmed with HDR in mind it's a benefit. Bummer things always get taken to the extreme.
99.9% of people expect HDR content to get capped / tone-mapped to their display's brightness setting.
That way, HDR content is just magically better. I think this is already how HDR works on non-HDR displays?
For the 0.01% of people who want something different, it should be a toggle.
Unfortunately I think this is either (A) amateur enshittification like with their keyboards 10 years ago, or (B) Apple specifically likes how it works since it forces you to see their "XDR tech" even though it's a horrible experience day to day.
The solution is for social media to be SDR, not for the UI to be HDR.
The "normal" video should aim to be moderately bright on average, the extra peak brightness is good for contrast in dark scenes. Other comments comparing it to the loudness war ar apt. Some music streaming services are enfircing loudness normalization to solve this. Any brickwalled song gets played a bit quieter when the app is being a radio.
Instagram could enforce this too, but it seems unlikely unless it actually effects engagement.