Supplier Shipping Configuration

I have one shipping method set up, and I've set it as the shipping method for every supplier (over 300).

This doesn't seem to work however, as on the 'edit shipping method' page, it shows up just for one supplier (has the store name then “(Default)” next to it).

The setting on the shipping method obviously seems to take precedence, but how do I get it so the shipping method is available for every supplier?

Removing all data in the 'shippings' column of the companies table seemed to have fixed this.

Still not sure why there are two separate ways to set the supplier shipping, while only one seems to actually work.