Google has issued a statement explaining what situations warrant the Pixel 4 and Pixel 4 XL automatically downgrading the display’s native 90Hz refresh to 60Hz. The statement follows reports of the newest Pixel phones switching to the lower refresh rate when the brightness level is below 75 percent, which will be addressed in a future software

Source: Hot Hardware – Google Explains Pixel 4 90Hz Refresh Rate Oddities, Says Software Update Coming