As a professional refurbished smartphone manufacturer supplier, we can definitely tell you that the answer is no! there is only manufacturer supplier.
Where are these manufacturer suppliers mostly located? they are located in TongTianDi Market of Huaqiangbei, Shenzhen City!
For Huaqiangbei electronic market, it is known as the biggest wholesale electronics market.but for TongTianDi Market, it is well known as second-hand mobiles and parts market.

The following photos for your reference

There are thousands of refurbished smartphone manufacturers in TongTianDi Market, some manufacturers are small sized with around 10-15 trained employees which are very good at refurbishing smartphones,and they usually focus on refurbishing few phone models or just one brand(such kind of manufacturers purchase the used mobiles and replacement parts from TongTianDi Market directly, They do not recycle)
some are large sized manufacturers with more than 100 trained employees(some of them to recycle second hand or used mobile phones, some of them to refurbish them, some of them responsible for marketing)

So if you are going to buy refurbished smartphones wholesale, we suggest you to cooperation with largely sized manufacturers like us, they have professional manufacturer team, QC team, marketing team.not only they have the better price, but also can avoid a lot of unnecessary trouble.