No, it doesn't. The Vega drivers vastly improved with each Mojave update. That's just the screwed up Geekbench benchmark. Don't use it.
FWIW, I have received a GB score nearly as good as my friend's 2012 cMP. Better in single thread, and a little worse in multithread. We have x5680s in our system. He has 2 and I have 1.
I have GB scores on my late 2013 MBP that exceed what I get on my cMP. But in real video work, the cMP is much faster and more capable.
Do something that's actually GPU intensive when benchmarking, like Unigine Heaven or Valley. Test each in HS and Mojave and post the results.
Do something that's actually GPU intensive when benchmarking, like Unigine Heaven or Valley. Test each in HS and Mojave and post the results.