[Bruno]

Smell includes a directional component that Taste does not. Snakes "taste" the air, but GURPS calls that Smell, not Taste because it works very like mammalian and avian smell.

Even in humans, we can taste things that are carried in the air, not just by touching them, but it's still quite different from Smell. It takes one heck of a strong signal to register at more than reach C for tasting, and we can't sniff it out the way we can with our noses.

Discriminatory Taste gives no sense of direction - like any signal detection device that gives magnitude but not direction, you can do a whole bunch of sampling in a grid and do math, or just play Hot-Or-Cold, to locate something, but that's really inefficient.

Sharks detecting blood a mile away and heading in the right direction is Discriminatory Smell (and the long-range smell perk), not Discriminatory Taste.