The author seems to speak to that here:

> SPy does something different: on one hand, it removes the dynamic features which make Python "slow", but on the other hand it introduces new features which make it possible to implement and use the same pythonic patterns which we like.

The author seems unusually focused on explaining his new way, which may help it feel more like a new language with a coherent philosophy and unique benefits in its own right.

Not unlike how Crystal isn't really "compiled Ruby" but rather its own language that just looks and feels similar to Ruby.