I think you need to restate your position, because I cannot quite understand it. I think you are saying that since the saints are saints, and the church is not stupid, that when a Saint is canonoized, that means De Facto that they are not guilty of material heresy or error. Because the Church is Holy, it cannot give sanction to impious writings.
Well, I hate to burst your Bubble, but that is false.
Let me tell you why:
We have two saints from the same era that co-founded heresies:
St. John Cassian, and St. Vincent of Lerins. They both contributed to the founding of Semi-Pelagianism, after Pelagius had already been condemned. They disliked St. Augustine.
Regarding St. Vincent of Lerins Catholic Encyclopedia Says:
"He was a Semipelagian and so opposed to the doctrine of St. Augustine. It is believed now that he uses against Augustine his great principle: "what all men have at all times and everywhere believed must be regarded as true". Living in a centre deeply imbued with Semipelagianism, Vincent's writings show several points of doctrine akin to Casian or to Faustus of Riez, who became Abbot of Lérins at the time Vincent wrote his "Commonitorium"; he uses technical expressions similar to those employed by the Semipelagians against Augustine; but, as Benedict XIV observes, that happened before the controversy was decided by the Church."
Regarding St. John Cassian: Catholic Encyclopedia
"Yet Cassian did not himself escape the suspicion of erroneous teaching; he is in fact regarded as the originator of what, since the Middle Ages, has been known as Semipelagianism. Views of this character attributed to him are found in his third and fifth, but especially in his thirteenth, "Conference". Preoccupied as he was with moral questions he exaggerated the rôle of free will by claiming that the initial steps to salvation were in the power of each individual, unaided by grace. The teaching of Cassian on this point was a reaction against what he regarded as the exaggerations of St. Augustine in his treatise "De correptione et gratia" as to the irresistible power of grace and predestination."
So here you have two saints in the Church who are considered the founders of a heresy.
I think your theory just exploded.
Saints are canonized for the HOLINESS OF THEIR LIFE, not for crossing every t and dotting every i theologically speaking, although that must always be considered.