In user manual mr. Pass writes: "The first version used diferential Mosfet circuits operated without feedback." But I am unsure, if it means entirely without feedback or only without global feedback as in AlephP 1.7.
The X-circuits in the big power amps (which only licensees of Nelson Pass can use provided patent holds and no workaround can be found) employ local feedback to around a single voltage gain stage. This is very similar to basic op-amp theory (but most op-amps have multiple internal stages, and feedback around these have become universally detested in audio).
Feedback is a method to reduce noise etc. Degeneration is generally considered the "least harmful". The next level, I will call feedback around single loop for lack of a better name, and this is the method used in the X-series power amps.
Feedback free amplifiers are like Yeti's -- many have seen them, but nobody can produce one.