AMD could likely allocate the resources, but what will they cut to do so? At this point they are a token competitor to Intel and are losing money and have been losing money for years, so how much of their financial runway are they willing to burn up on a platform that doesn't use them for servers and minimally uses them for gaming (where the platform has no marketshare).

I as a full time debian user for the past few years get it. AMD's Linux devs heavily dislike direct rendering manager and want to provide all the cool crap their proprietary driver does to Mesa, cause DRM is legacy tech and they have over 1000 SKUs of cards to support, 2 competitors breathing down their neck on both the GPU, CPU and SOC sides, and they wanna get this shipped.

I hope I've illuminated the state of the situation for you, I do think the right decision was made to not merge this code, but be realistic about AMD's position, they are so far in the hle financially that customers are having chips made to order after paying, meaning its at least 3 months from the time f order until you get your chip. They spend nearly all that time making the silicon, then packaging it so it can go onto your motherboard.