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davidcyclebackIn general, if a CDV was used for commercial/advertising purposes, it will be considered a trading card-- add on back, sold at stores or in catalogs. For example, the Peck & Snyder cards can be found both with advertising and were sold to the public via the P & S catalog.
The problem is it's often impossible to know how a CDV was distributed-- commercial purposes or just a studio photo. Typically, a CDV is called a baseball card if it is known for certain the card was a commercial item. And if you don't know, you don't know.
There are cases where a CDV or cabinet was made by a photographer known to have sold his celebrity photos to the public-- Mathew Brady, Sarony and others. Brady and Sarony had galleries were the public could buy photos. With these photographers, it's more likely the item was a commercial product, even if there is no advertising or other signs. If you own a Napoleon Sarony cabinet card of James Jeffries, it likely was a commercial product offered to the public, and is as much a trading card as a T5 Pinkerton cabinet.
For the eBay CDVs, it is relevant that they show the players formally posing in their uniforms. At the least, they are formal team photos.