Seller Support, so-called, is completely worthless in matters of policy.
Amazon is a self-learn venue. The Help button at the top right of any Seller Central page has all the policies, help files and videos pertaining to all Amazon practices and how-tos.
You were misinformed about what a Pro account is. It is a full featured Amazon membership allowing you to access uploade templates, be eligible for the buy box, have an actual storefront, plus avoid the extra 99 cent per item fee that individual sellers pay.
DVDs is a gated category. Many Amazon categories are gated. A Pro account allows you to apply for those, and if approved, to sell in them. Individual sellers are restricted to open categories.
For DVD approval you pretty much have to have a B&M store, buying direct from major media suppliers.
Here is more detail on a Pro account from the Help files:
[Selling plans|https://sellercentral.amazon.com/gp/help/help.html/?itemID=64491&ref_=ag_64491_h_r0_bc_cont_sgsearch|Selling plans]