You are overgeneralizing. Clark himself advocated synergistic sanctification. The point of my quote is that even Clark is inconsistent here. And the further point is that even Calvinists who advocate synergistic sanctification are not advocating libertarian free will or any other such thing. That's because free will does not exist even in the regenerated elect. That's obvious because even the regenerate continue to sin both voluntarily and involuntarily in this life. They only become sinless in glorification.

For "who has known the mind of the LORD that he may instruct Him?" But we have the mind of Christ. (1 Corinthians 2:16 NKJ)