Okay, after another bout of !!Science!!, I've discovered a bit more on attributes and their relationship to transformations. It seems that when you undergo a transformation, your physical attributes are randomly generated for you new body, but your mental attributes remain the same. This actually makes a lot of sense, since you have the same soul but a new body.
The part that confused me is that your mental attributes are described in terms of the average of your new species, rather than your original. Most of my tests were arena-mode humans turning into a custom creature I made. This creature's focus, willpower, and several other mental stats had a higher average than humans, so whenever the humans transformed, these were always described as low, since they were average for humans. I originally thought the change was caused by the randomization of their attributes, but it's been consistent for all the transformations I've witnessed.
This also means that my research on attribute gains/losses between forms isn't relevant anymore. I know now that mental attribute gains/losses are kept between transformations since, but I don't know if physical attribute changes carry over between forms. I think I'm going to hold off on testing this until Runesmith or another utility is updated for the current version, since the !!science!! will be more accurate if I can see the actual numbers rather than just a high/low/average description.