Back in June 2012 the HD7970 1Ghz did 1 TFLOPs FP64 at $500.
AMD only started to artificially strip down FP64 throughput with Hawaii.
I doubt a 1:2 FP64 Radeon VII was ever going to cannibalize the MI50. The MI50 is apparently only selling inside specialized server stacks or even full server towers, so I wonder if this is really a valid concern.
Within the compute community, AMD cards have the considerable disadvantage of not running CUDA, so AMD couldn't ever ask the same money as a nvidia counterpart just for parity on floating point performance.
That's where a 1:2 FP64 "prosumer" Radeon VII made sense: gain market from nvidia for the cost/performance disparity and get those people to start using ROCm supported languages.
Is Radeon VII really a consumer card? AMD sure seems to be pointing the card at the prosumer "niche" by constantly mentioning content creators.
I'd look at the VII as a consumer card had they cut down FP64 throughput, cut the memory stacks down to 3 for 12GB/768GB/s (or even 2 stacks of 2.4Gbps Aquabolt for 8GB / 614GB/s) and raised the core clocks by 5-15% compared to the Instinct equivalents.
The end result seems to be a product that doesn't really fit either a Pro card nor a prosumer nor a consumer one. Sure performance is on par with a RTX 2080, but that 4th HBM2 stack seems to be just taking space and increasing BoM IMO. It's not like the perception of value was ever going to significantly increase between 12 and 16GB VRAM, and I bet the bandwidth delta only really benefits heavy FP64 computations.. which the card apparently can't do either way.