No, on actual paper one is darker and more saturated than the other. Unlike RGB, CMYK is subtractive, so “all of everything” gives you black, not white.
Digitally these should be equivalent. Physically, I'd assume it's just as likely that adding CMY pigments would dilute the K and make it less purely black - but, per link you shared, it seems it's the opposite, and I didn't even realize this is an actual technique. Thanks for posting!
