This was probably Apple just not wanting to have their M2 machine being out performed by a previous machine, and to try and ensure that people will throw away more big $$$, which I refused to do.
Probably not. It is likely driven by the fact that the rest of the Mac line up dropped AMD GPUs. There is no unit volume to support the driver development for a new GPU implementation.
The 580 in the initial MP 2019 was a 'Polaris' class GPU that was used in other Macs ( ).
580X in 2017
The 5000 series was used in the iMac 2020 and MBP 16" 2019
support.apple.com
support.apple.com
Vega II is a follow on to Vega used in Mac Pro ( there is some unique work there).
support.apple.com
The Mac Pro got 6000 series probably Apple knew they were going to try to do the Mac Pro at the end of the two year transition and just needed some 'fill' to kick the can down the road. Also partially driven by problems that Vega II presented ( AMD skipped a 'large GPU' solution for the 5000 series because of birthing hiccups in their GJP family development). The 580 was also 'old' on day one also. Essentially, got a bump there because AMD didn't deliver on time. ( AMD probably soaked up a sizable chuck of costs for that just to hold onto the declining contract just to keep a steady customer with deep pockets. )
Apple likely told AMD way in advance that Mac Pro 2019 would drop from market in late 2022. That probably changed to 2023 later, but the Mac Studio would have been out by then it the writing on the wall in bright neon lights for AMD. At that point, if no new systems being sold what is the market 7000's? Relatively not much ( in context of crypto and then AI mania crazes ).
It isn't tech benchmarks porn numbers that stop new dGPUs. It is just plain economics. If Apple isn't spending any money on it then AMD isn't going to either. AMD subsidizing Apple is nuts. [ If AMD unilaterally did the drivers then most MP users would buy the Windows PC market version of the cards and AMD would recoup little to none of the money spent. So yes, that would be an Apple subsidy. ]
It is the same detachment with the notion that Apple could just keep macOS on Intel going forever with zero new product being sold on that platform. When the rest of the mac line up dumps dGPUs... the Mac Pro pushing that up the hill all by itself doesn't work.