While this is true, you can compensate for it by adjusting the color to shift into a more neutral white. E.g. if it’s giving you a cold / blueish white, then adjust warmer. Your laptop makes white using RGB. How good you can get it depends on the RGB implementation, how fine the adjustment steps are, and if there are enough steps at the brightness level you want.
With QMK, if you use extremely bright WS2812 LEDs you don’t have a lot of steps at very dim brightness levels & you can’t do precise mixing. I recall seeing in Framework’s code that they’re using a different RGB driver. Hopefully they also don’t use extremely bright LEDs, no need to get a suntan off your keyboard. When you say most RGB keyboards are bad at making white light, you need to try a QMK one with well selected RGB LEDS, or at least having a reasonable max brightness (not artificially limited in code). It makes a difference. It’s also possible in QMK to just have a separate white-led backlight. I saw a separate backlight pin defined in Framework’s code, I just don’t know what they are using it for.