I agree with this statement. The Mutant Filter is based on what many consider to be one of the first first and favored auto-wah pedal - considered to be categorized in the "envelope" filter family of effects pedals - The Musictronics® Mu-Tron III which was introduced in the mid-1970's. The Mutant Filter (Musictronics Mu-Tron III) allows you to adjust the effect based on your picking attack and several other factors.
Here are some links to videos that demonstrate what the Mu-Tron III could do as well as the history behind the Mu-Tron III pedal.
Mu-Tron III on Wikipedia - https://en.wikipedia.org/wiki/Mu-Tron_III
That Pedal Show – Introduction To Auto Wah & Envelope Filters - https://youtu.be/Dp1s0Ow2BJU?t=427
George Duke - Mutron, demonstration record 1975. - https://youtu.be/wEdXlMqD5BI?t=217
Battle Of The Trons! Mutron III vs ULTRON vs Tru-Tron3X - https://youtu.be/ZcTkTKKBcsE
