Okay folks, it looks like I've gotten a little bit closer of an answer as to why there is no acceleration for the AMD Picasso on macOS despite being present since Catalina 10.15.4 beta.
One thing that I did not realise, is that the Picasso card also has the same PCIID value as Vega 11 series.
Here is a screenshot of the Vega 11's device properties for Windows I found online, whose device id matches the Picasso:
When we look at the AMDRadeonX5000 kext from Monterey we find that it has builds for Vega 10, Vega 12 and Vega 20 but nothing for Vega 11.
So now that we have this info, what does it all mean? It means the Picasso IOKitPersonality ID was never included in the final macOS kext builds after the beta version and that technically we should be able to inject our very own Vega11 IOKitPersonality into the Info.plist to include this info to allow for acceleration. So I will be testing this soon!