Steps to reproduce with attached save file:
1) Verify that current brand strategy is set to "Range brand"
2) Look at the product list of my corporation and see that all the products are listed as having a "Unique brand" instead of a range brand.
3) You can even try changing brand strategy to "Coroporate" and current products will still stay as "Unique brand"
I started a new game and set brand strategy to "Range", only to later find out the products I was selling were uniquely branded regardless.
Thank you very much for your help, I am enjoying the game so far

EDIT: Hmm, if I produce a product (like with my own farm), THAT product is listed as having "Range brand". Maybe imported goods are forced to be "Unique branding" ? But if so, how does it make sense that I'm paying thousands to advertise a brand I do not own?!