If they decide to not let it run at 4K, then let them, benchmarks with comparable cards show the performance is there, what ever reason they decided is what they decided.
It is strange for a GPU (polaris) is not a 4K card from the get go as its only 4 CU above the desktop equivalent and that was literally targeted as a 1080p card from AMD to a card (Navi) which on desktop is a 1440P targeted card (esp with a new arch this time round), let you take that as you will.
Would not surprise me if down the line this changes.