I always test products, even if they've been around for years - because they are being manufactured from scratch. Eg; everything gets tested, apparel, weightlifting belts. Testing over and over again. I am quite picky, and will not get something manufactured unless it is good.
When you're manufacturing your own brand, you don't resell others' products - which can be bought in a smaller quantity. When we get something done up, it is done in the 1000s not 100s. Hope this makes sense!
So things like material, sizing, comfort, durability etc all come into play prior to production.