I can't see how they would help with any part of the process. They would not cover THC being released in urine from the blood stream. And they cannot absorb THC from the lipid tissue while the charcoal is merely in your stomache.

I'd say charcoal tablets are bunk.

They are not given to induce vomiting (although sometimes they do). They are given to adsorb chemical poisons that have been ingested and so prevent them from entering the body.

If you become poisoned, the charcoal will act as a sponge and absorb the toxin.

The capsules will dissolve quicker and thus go to work faster. Capsules probably cost more.

Bloodstream