In general, the unsaponifiable part of an oil is always the one that resists soap making. If you want to know more about this, we have written a short explanation about what can and cannot be saponified in an oil at sunflower oil unsaponifiables (2nd paragraph).
Avocado oil contains much more (about 5-12%) unsaponifiables than most other oils, which is only 1-2% of oils usually. The major components in the unsaponifiable part are skin nourishing and soothing sterols (β-Sitosterol mainly and some campesterol) and the most potent antioxidant type of vitamin E, α-Tocopherol.
Show me some proof
- Lipids, Sep 1, 1974, Studies of unsaponifiables in several vegetable oils