That’s not true, though. You can have 100% olive oil, 0 superfat, and no suds.
Bubbly lather comes from coconut oil, castor oil (up to 5% in a batch), and some other oils, but the amount of superfat isn’t part of it as a rule.
For example, I LOVE spa bars. They are salt bars, 100% coconut oil (or 95% coconut oil and 5% castor oil), 50% fine sea salt by weight of oils, and superfatted at 25%. Bubbly rich lather than is creamy and fabulous. But coconut oil is well known for bubbly lather.
Now, sometimes too much SF may indeed inhibit lather, but it’s not really a part of the calculation as that is not true in many (or even most) cases.