Also, if a saint inadvertently teaches something wrong, and then he finds out that the Church has ruled the other way, he will accept the Church’s teaching over his own.
That said, there’s nothing wrong with arguing hard up until the last moment! A lot of saints have!
For example, St. John Newman. Didn’t like the definition of papal infallibility. Didn’t like the definition of the Immaculate Conception. Swallowed his pride and let the Church be his guide.
If you ever see a theologian saying, “I submit all this to the judgment of the Church,” that’s what they’re doing ahead of time - saying they’re prepared to be found wrong.