It appears this weird card is designed for cryptocurrency miners. We didn't expect to see much crypto-specific hardware since as crypto market has totally collapsed, but it looks like Sapphire still sees some valuable target markets:
Sapphire in its response said that they wanted to bolster the card's crypto-currency mining power, and giving the "Polaris 20" GPU additional memory would improve its performance compared to ASIC miners using the Cuckoo Cycle algorithm. This can load up the video memory anywhere between 5.5 GB to 11 GB, and giving the RX 570 16 GB of it was Sapphire's logical next step. Of course Cuckoo Cycle is being defeated time and again by currency curators. This card will be a stopgap for miners until ASIC mining machines with expanded memory come out, or the proof-of-work systems are significantly changed.
Via: TPU