Michael Baius presented the history of humanity with the terms: (1) the state of innocent nature; (2) the state of fallen nature; and (3) the state of redeemed nature. Notice how Baius refers to these states as various "natures". Herein lies the error.
Baianism is a strange blend of confusion. Baius is Pelagian with respect to (1) the state of innocent nature; Baius is Calvinist with respect to (2) the state of fallen nature; and Baius is Lutheran with respect to (3) the state of redeemed nature.
(1) Baius on the state of innocent nature
Baius conflated nature and grace in the original man so that in Adam sanctifying grace and the preternatural gifts (immortality, infused knowledge, and integrity of passions) were natural and not gifts. In other words, Baius thought that man was naturally immortal and naturally destined for the beatific vision of Heaven.
Consequently, Baius' doctrine is a Pelagian understanding of pre-fallen man - Baius taught that Adam was essentially graceless prior to the fall.
(2) Baius on the state of fallen nature
As a result of Baius identifying grace and the preternatural gifts with "human nature", men must necessarily fall from human nature.
In Catholic soteriology, man falls from grace and the three preternatural gifts (immortality, infused knowledge, and integrity of passions). Since Baius imagined pre-fallen Adam as naturally possessing these attributes, Adam fell from his own human nature. Adam possessed a depraved nature or a sinful nature. It is state of total depravity.
(3) Baius on the state of redeemed nature
Baius comes close to Luther in this aspect because justification is merely a fictio iuris ("legal fiction"). Since mankind possesses a depraved nature and is not fully restored to the pre-fallen state of innocence in this life, it is therefore impossible for an interior renovation to occu within a believer's soul.
Baius believed that his doctrine would attract the Protestant "heretics" and that his theology was more faithful to Sacred Scripture and the Church Fathers. He is right that his doctrine of salvation does come close to Luther and Calvin's "justification by imputed righteousness". Nevertheless, Pope Pius V condemned seventy-nine propositions from the works of Baius as heretical in his 1567 bull Ex omnibus afflictionibus.
All this is to show that one's doctrine of salvation is intimately bound to how one understands grace, nature, and the state of mankind prior to the fall.