Personal perception. The drier it feels, the cleaner it feels. Whether accurate or not, when I feel oily or moist skin, it feels dirty or sweaty to me. Quite unpleasant. Dry skin though feels quite clean, long as it's not so dry it's cracking and bleeding. That would be bad.
Shalisk finally made up a small batch of the 100%CO-76deg/0%SF for me. I'm letting it cure for another week before I try it (as hard as it is already, I figure two weeks will be plenty). Really looking forward to seeing just how dry this can get my skin. If it works well, I might buy him some fractionated coconut oil for the next batch.
As has already been mentioned, when you strip all of the skin's protective layer of natural oils off, it works that much harder to produce MORE oil to try and regain its protective layer. To reduce this, use a less harsh soap. It does not have to leave your skin "moisturized" or oily-feeling, but it shouldn't leave your skin overly dry either.
My husband likes a 100% lard soap with only a 3% superfat. It gets his skin "squeaky clean" like he likes it, but without overly drying and irritating it.
Coconut oil and lard are the two most commonly used oils for homemade laundry bars. they both are very effective at removing dirt and excess oil. The coconut oil just has a difference of opinion with most people about what it considers to be excess lol.
Also, as mentioned, longer cure time makes for a longer-lasting bar with better lather.
BUT, your bar is 100% coconut, which is very water soluble, and dissolves fairly quickly with use, compared to soaps with lower coconut content. Lard on the other hand, does not dissolve as quickly, and can give you the squeaky clean feeling you're looking for, in a long-lasting, hard bar with good lather.