No, an article on one's website describing why one no longer considers JPII the legitimate Pope of the Roman Catholic Church is good enough earnest of one's sedevacantism.
The article is nevertheless a valid and coherent expression of what's wrong with JPII's approach to the faith. The fact of Derksen's recent conversion to sedevacantism--this article was written two years ago--in no way invalidates the cogent argument he presents.