From my point of view - it is only hypo if the colour is lighter due to a defective genetic condition that results in less melanin production than the snake ordinarily would have.

Variations in the base colour of cal kings exist throughout the range.

I think one of the determining factors when the term is used properly is the coloration when they hatch. I do not know if this is universal or not, but in every place I have herped with brown adult cal kings, they hatch black and the color changes to brown as they grow up (though often the head remains very dark).

If a Cal King is truly hypo, and this is me speculating, it will not be black base colour when it comes out of the egg.
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3.6 L. getula californiae - 18 eggs (Cal. King)
1.1 L. getula nigrita (MBK)
1.0 Pantherophis guttatus guttatus (Corn)
0.1 Pituophis catenifer catenifer (Pacific gopher)
3.3 Elgaria multicarinata multicarinata (Cal. Alligator Lizard)