Yep, to put it in practical context, 6500 is there so that if you have a texture, where certain pixel when measured in photoshop has say RGB 210,80,20, and you map this texture to self illuminated or emissive plane with multiplier of 1.0 and you do not touch exposure, if you measure same place of the map on the output render, it will still remain RGB 210,80,20. So by default, your colors are not modified in any way.
If default was 5500k, then imagine what a chaos it would make if you would make white wall material, yet it would render light blue under neutral light conditions :)