I'm sure that's true, at least how it's designed. I read here on BYC where the eye dropper method augmented with enhanced water was recommended by one of the regulars, and since I still had dying chickens after two courses of Corid the recommended way I tried it. It wasn't like they were going to live otherwise, and I was desperate (I started a thread about it with no response). So far, of the four I've given this treatment, three are not only alive but now appear healthy. The fourth was too weak when I started this routine, and was past helping.
So, take it with a grain of salt. My advice is worth every penny you paid for it. All I can do is share my experience, and obviously if any negatives come out of this I will post them, too. The real key is prevention, and while it's not possible to completely eliminate the risk of coccidiosis, at least we can lessen the likelihood.
Actually I agree with your giving the Corid orally in a concentrated form, along with water supplementation. It's just that I wanted to let you and others know that it is normally given in the water. I would also have done what you did. Some newer people read only a few threads and may get the wrong information if it is not clear--that's all I meant in pointing it out. Casportpony has done a lot in educating people about Corid dosage and giving it in a concentrated form. The manufacturers don't help much in their directions, since Corid is many a drug for cows and other large animals.