Hexus posted a review on the Sapphire Radeon RX Vega 64 Nitro+
A quote from the article:
Air-cooled Vega done right? The AMD Radeon RX Vega GPU was trumpeted as a serious challenger to the dominance displayed by Nvidia's range of premium GeForce cards. RX Vega did come in, eventually, released in reference form during August.Sapphire Radeon RX Vega 64 Nitro+ Review @ Hexus
One would have expected partner models to arrive on shelves very shortly afterwards, differentiated on cooling, design, and performance, but this did not happen. In fact, even four months after launch, the only models of RX Vega that you can buy are based on reference air- and water-cooling designs from AMD.
Why? That is a question with many possible answers, and the one that appears to fit best is that AMD has been slow to release Asics and board designs to customers such as Sapphire and Asus. AMD has missed a serious monetisation opportunity in the run-up to the holiday season, but as the adage goes, it's better late than never.