Hey your right, this is a game with a lot of peak white points.
This is called ABL/ABSL, or known as Automatic Brightness limiter. All OLED’s have this issue, actually in fact, most TV’s have some kind of “auto dimming” feature, when HDR content is so bright that it’s causing the TV’s panel and power supply to run too hot, it automatically dims, even on high end LCD TV’s. Take the Samsung QLED’s, it’s called Global Dimming and it can be brutal in game mode. Just one search of Samsung QLED Global Dimming on Google, you’ll find thousands of threads from angry gamers.
Unfortunately practically every TV has this too a degree, it’s so that the TV manufactures can get the best performance out of the TV’s when reviewers calibrate them, however it’s similar to running a car at 100% throttle the whole time, your likely to do some damage if your doing that every day. And since HDR is naturally designed to “max out” your display, that’s when ABL/ABSL/Global Dimming comes into play.
This is to protect the life of your screen/panel and make sure that it lasts you for the next 5-10 years. It is especially more important on your OLED because of burn in.
Unfortunately as you already know, the only way to disable this is to go into the TV’s service menu. That is the only way to disable ABL/ABSL. However there are hundreds of not thousands of threads online of how to disable this on your OLED, in fact many gamers tend to disable this feature, because it becomes very annoying and ruins the HDR experience. I’ve done it on my OLED, no issues here, just more careful and cautious to not “overdo” it and binge game FIFA for 18 hours straight.
The only panels I know with relaxed ABS/ABSL on OLED’s are either the LG G1 OLED with the new EVO panel, which is more efficient in design, so it draws less power, which equals less heat and less likely for burn in, so more relaxed ABSL as well. I know the Sony A90J OLED’s as well as the Panasonic JZ2000 also have the new EVO panel as well, and they also have an additional cooling heatsink, so their ABSL is even more relaxed.
But again, every TV regardless of wether it’s OLED or LCD will have some kind of built in brightness limiter that can only be turned off in the service menu.