I'd say give it time, things are being worked on but it takes time and as you may have guessed. Not everyone who had a 7 pro would have felt like getting the 8 pro, personally I think it's a worthy upgrade.
Or they may have moved to the pixel or elsewhere.
I think once TWRP is sorted, a few more Devs will jump ship and we will see more.
For now I don't believe we have this functionality.
Would the version you had on the 7 pro work for the 8 pro? Might be worth asking the original Dev about.