I obtained very similar results when measuring OLED iPhones 3-4 years ago: close to 6500 K but slightly on the warm side (i.e. 6400-6500 K), and the LCD iPhones were cooler, more around 6700-6800 K.
LCD displays traditionally have a cooler white point. LCD backlights used to be 9300 K natively (maybe still are?), possibly because that’s the white reference mandated by NTSC-J. The further away the configured white point is from those 9300 K (i.e. compensated by pixel colors), the more the display loses contrast and color range. This may be the reason why “neutral” (nominally 6500 K) white points on LCDs tend to be slightly more on the cool side.
That being said, I’m not entirely sure how neutral the 6500 K standard really appears to everyone. For one, there is likely some individual variation, and secondly it’s not clear (to me) how exactly the 6500 K standard was arrived at to be declared the most neutral, i.e. what the accuracy of that number is with respect to what people actually perceive as neutral white.
In addition, the factory calibration process for OLED seems to be less accurate than the differences the human eye can perceive. Whenever I have compared multiple units of an OLED model, the color temperature was never exactly the same between them.