Here are my random contributions / ideas / theories for whatever they're worth ... because I think discussions like this can lead to some incredible insights!
I use SoapCalc all the time simply because it's what I got used to using and might as well stay consistent so I'm comparing apples to apples. I quite like it but I also know it has limitations. So I really get your frustration Kat ... I'm like you in that I want understand HOW and WHY soap acts like it does in the shower ....as per its
formulation.
I tend to think that palm oil and olive oil screw with everything ...but in a good way

. Here's why I think that:
Palm oil may be considered a "filler oil" by some soapers but I beg to differ. Maybe it doesn't impart major benefits to your skin when it's saponified
all on its own, but in synergy with other fats it makes a world of difference to the feel, and it lends a true
creaminess to soap. That said, if you used lots of palm oil but the
rest of your formula/ingredients is blah ... well then I think it's just gonna be a blah soap, even though palm rates high-ish for creaminess. But a generous helping of palm with a strategic combo of oils/fats makes GREAT soap.
Olive oil is the other wild card to my mind. For e.g. SoapCalc makes castile look like a miserable failure, yet we know that's not true, especially if it's made with a steep water discount and left to cure for a long time. (Yes, opinions vary but generally speaking, castile is a pretty great soap and seems to be a staple in many a soaper's product line.)
But where it gets weird is that OO makes your soap feel creamier yet only rates 17 for "creamy" in SoapCalc.And for whatever it's worth, castor oil rates extremely high for creaminess but I think you need something "hard" to really "deliver" that experience in the water. Otherwise it's just kind of a mushy mess.
When I look at the SoapCalc numbers for the
individual fats (first column) it takes some of the mystery out of it. I believe that all SoapCalc is doing is taking a
weighted average of these numbers to give us the overall rating for each of hardness, cleansing, etc.
Though you can be sure someone somewhere is working on an algorithm to factor in how variables like water discount, temps, etc factor into the resulting qualities of the soap! It won't be perfect but I'm willing to bet soapers will flock to it. (Anything that reduces uncertainty -- even in testing -- reduces time to market and is going to be a success.)
I think that oils/fats behave differently based on how they're combined and "soaped" and SoapCalc doesn't really take those things into consideration. So OO isn't "creamy" per SoapCalc, yet if you add it to some other oils/fats it somehow
does feel creamy in the shower (and I'd also bet that some testers are going to say that slime is "creamy" in their feedback, even though we soapers may not).
Then there's the fact that people interpret soap qualities so differently. I had a tester say my palm-free soap felt like
lotion in the shower. She
loved it. I personally thought it was blah. I've also had people say they loved some of my earlier soaps that had 50+% palm. So go figure right? So much is in the "skin of the beholder."
Karri