Yes really, for hystrix the spine color is extremely deterministic going towards yellows.
Also the hystrix you link to has already developed ribs which the plant in the OP has not, while it is of similar size, that is another clear indication that the plant in the OP is not hystrix. I am too lazy to go take a picture but I have a similarly sized covillei which is in most cases considered a ssp. of emoryi, that looks pretty much exactly like the plant in the OP. See the horizontally oriented white spines on that plant, that is a pretty diagnostic feature of F. emoryi ssp covillei. New spines on covillei start out very reddish and then slowly go towards mostly grey, but it has two horizontally oriented spines that are white which stay that way for quite some time before also fading to grey.
The plant in the OP is not hystrix, simply isn't.