Its already been mentioned a few times on the forum that the 290.7 reading was a writing error that hasn't been amended.
Link example - post 2838:
Eye-strain while using iPhone X
Yes I mentioned earlier in this thread that the original review was bogus as they misread their own graph. It clearly shows slower than 290hz if you measure it yourself, but they wrote the 290 anyway. Sloppy. Also this goes to show how much this issue is placebo induced that merely the...
The report also mentioned:
11 Pro Max:
"The display backlight flickers at 245.1 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 99 % and below. There should be no flickering or PWM above this brightness setting.
The frequency of 245.1 Hz is relatively low, so sensitive users will likely notice flickering and experience eyestrain at the stated brightness setting and below."
11 Pro:
"The panel in our review unit flickers at between 60 and 290.7 Hz,
which is rather unusual. By contrast, most OLED panels flicker at one frequency."
🤷♂️