That is just more Lost Cause mythology. Here's a good article that dispells that myth.
I read the article at your link. It rebuts nothing. It asserts 29 million dollars worth of wool imports balances the ~300 million dollars in Southern Agriculture product exports because Northerners wore wool.
It is an analysis written by a child, not someone seriously addressing the issue. It is the opinion of someone intent on dismissing the claim without putting forth any real effort to discredit it, knowing full well that the vast majority of his Union supporting audience wouldn't bother to critically dissect his claims.
There is a simple fact that remains. Imports coming into the Country have to be paid for by Foreign money received, and since that comes mostly from Domestic exports, you have a conundrum explaining how all the Northerners got all that European money to pay their share (80%) of the tariff duties on imports.
Since Southern Agriculture products made up 75% of exports, where did the Northern states get their European money?